Patent Publication Number: US-11391504-B2

Title: Refrigerator

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese Application JP2019-082593, filed Apr. 24, 2019, the content to which is hereby incorporated by reference into this application. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     An aspect of the present invention relates to a refrigerator including a refrigerator compartment mainly cooled by direct-cooling. 
     2. Description of the Related Art 
     Techniques for cooling refrigerators include direct-cooling and indirect-cooling. In the direct-cooling, a refrigerator has a metal cooling plate provided to, for example, an interior wall of the refrigerator. This cooling plate is cooled with an evaporator in a freezing cycle. Hence, the inside of the refrigerator is cooled through the cooling plate. In the indirect-cooling, the air is cooled by heat exchange with an evaporator in a freezing cycle, and the cooled air is blown to the inside of the refrigerator with, for example, a fan to cool the inside. 
     Compared with the indirect-cooling that involves circulating the cooled air with a fan, utilizing the direct-cooling to cool the inside of the refrigerator is advantageous since the latter can keep the inside from drying. Meanwhile, utilizing the indirect-cooling to cool the inside of the refrigerator is advantageous since the inside can be cooled quickly. Some refrigerators cool the inside utilizing both the direct-cooling and the indirect-cooling. 
     For example, a refrigerator disclosed in Japanese Unexamined Patent Application Publication No. 2000-356445 cools a refrigerator compartment by direct-cooling and a freezer compartment by the indirect-cooling. 
     SUMMARY OF THE INVENTION 
     In cooling vegetables in a refrigerator compartment, the inside of the refrigerator compartment is desired to be maintained at an appropriate humidity in order to keep the vegetables fresh. Hence, to cool a refrigerator compartment for vegetables, suitably adopted is the direct-cooling capable of further keeping the inside from drying. 
     However, if foods with a high water content at a relatively high temperature are put in the refrigerator compartment, a large amount of water vapor is generated inside the refrigerator compartment. The water vapor causes a problem of condensation on a cooling plate provided inside the refrigerator compartment. 
     An aspect of the present invention is intended to provide a refrigerator capable of reducing formation of condensation inside a refrigerator compartment while curbing a drop of humidity in the refrigerator compartment. 
     A refrigerator according to an aspect of the present invention includes: a first cooler; a freezer compartment an inside of which is cooled by circulation of cooled air subjected to heat exchange by the first cooler; and a refrigerator compartment cooled by direct-cooling, using a cooling plate. In this refrigerator, the cooled air subjected to heat exchange by the first cooler is to be supplied to the refrigerator compartment. 
     The refrigerator according to an aspect of the present invention may further include a temperature-humidity sensor configured to detect a temperature and a humidity of the refrigerator compartment, wherein the cooled air subjected to heat exchange by the first cooler may be supplied to the refrigerator compartment if a dew point inside the refrigerator compartment rises higher than or equal to a predetermined temperature. 
     The refrigerator according to an aspect of the present invention may further include a second cooler configured to cool the cooling plate, wherein the predetermined temperature may be lower than a lowermost temperature of the cooling plate. Here, the lowermost temperature of the cooling plate may also be referred to as a temperature of the cooling plate when the cooling of the cooling plate stops. 
     In the refrigerator according to an aspect of the present invention, the supply of the cooled air, subjected to heat exchange by the first cooler, to the refrigerator compartment may stop if the temperature of the refrigerator compartment falls below the predetermined temperature. 
     In the refrigerator according to an aspect of the present invention, the supply of the cooled air, subjected to heat exchange by the first cooler, to the refrigerator compartment may stop if the humidity of the refrigerator compartment falls below a predetermined humidity. 
     In the refrigerator according to an aspect of the present invention, the refrigerator compartment may include: a low-temperature room a temperature of which is set low; and a high-temperature room a temperature of which is set high, and the cooling plate may be provided in the low-temperature room. 
     In the refrigerator according to an aspect of the present invention, the low-temperature room may be provided with a temperature-humidity sensor. 
     The refrigerator according to an aspect of the present invention can reduce formation of condensation inside a refrigerator compartment while curbing a drop of humidity in the refrigerator compartment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view illustrating an internal configuration of a refrigerator according to an embodiment of the present invention; 
         FIG. 2  is a schematic diagram illustrating a configuration of a freezing cycle provided in the refrigerator shown in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view illustrating a configuration of surroundings of a refrigerator compartment in the refrigerator according to a first embodiment; 
         FIG. 4  is a flowchart showing a flow of processing to control temperature and humidity inside the refrigerator compartment of the refrigerator according to the first embodiment; 
         FIG. 5  is a cross-sectional view illustrating a configuration of surroundings of a refrigerator compartment in a refrigerator according to a second embodiment; 
         FIG. 6  is a flowchart showing a flow of processing to control temperature and humidity inside the refrigerator compartment of the refrigerator according to the second embodiment; 
         FIG. 7  is a cross-sectional view illustrating a configuration of surroundings of a refrigerator compartment in a refrigerator according to a third embodiment; 
         FIG. 8  is a flowchart showing a flow of processing to control temperature and humidity inside the refrigerator compartment of the refrigerator according to the third embodiment; 
         FIG. 9  is a graph illustrating temporal changes in temperature and dew point of compartments and a cooling plate, and states of components in the refrigerator according to the third embodiment; 
         FIG. 10  is a cross-sectional view illustrating a configuration of surroundings of a refrigerator compartment in a refrigerator according to a fourth embodiment; and 
         FIG. 11  is a flowchart showing a flow of processing to control temperature and humidity inside the refrigerator compartment of the refrigerator according to the fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Described below are the embodiments of the present invention, with reference to the drawings. In the detailed description that follows, identical constituent features have the same reference numerals. Such constituent features have the same name and function, and the details thereof will not be repeatedly elaborated upon. 
     First Embodiment 
     Overall Configuration of Refrigerator 
     Described first is an overall configuration of a refrigerator  1  according to this embodiment, with reference to  FIG. 1 .  FIG. 1  illustrates an internal configuration of the refrigerator  1 . The refrigerator  1  is provided with a thermal insulation box  50  acting as a thermal insulation structure to thermally insulate storage spaces from an environment around the refrigerator  1 . The thermal insulation box  50  is provided to cover an outer periphery of the refrigerator  1 . The thermal insulation box  50  includes therein the storage spaces such as a refrigerator compartment  11  and a freezer compartment  12 . The refrigerator compartment  11  and the freezer compartment  12  are divided by a thermal insulation division wall  52 . 
     In this embodiment, the refrigerator compartment  11  and the freezer compartment  12  are respectively arranged in an upper portion and a lower portion of the thermal insulation box  50 . Note that the arrangement and the configurations of the storage spaces in the refrigerator according to the present invention shall not be limited to the above ones. The refrigerator compartment  11  may further be divided into two or more storage spaces by storage cases such as a vegetable case and a chilling case and by divider shelves. 
     As illustrated in  FIG. 1 , the refrigerator  1  is provided with open-close doors (a refrigerator compartment door  11   a  and a freezer compartment  12   a , for example) in front of (in the left of  FIG. 1 ) the storage spaces. 
     In this embodiment, a face to which a door is provided is referred to as the front face of the refrigerator. Then, with reference to the front face, the refrigerator  1  has such faces as a top face  1   a , a side face, a back face  1   c , and a bottom face  1   d  (see  FIG. 1 ). 
     Configuration of Freezing Cycle 
     The refrigerator  1  includes therein a freezing cycle  20 .  FIG. 2  illustrates a configuration of the freezing cycle  20 . As main constituent features, the freezing cycle  20  includes: a freezer compartment evaporator (a first cooler)  21 ; a compressor  22 ; a condenser  23 ; a first capillary tube (an expander)  24 ; a valve  25 ; a second capillary tube (an expander)  26 ; and a refrigerator compartment evaporator (a second cooler)  27 . These constituent features are connected to one another through a refrigerant pipe  31  conducting a refrigerant. Operating states (such as ON/OFF and open/close) of the constituent features in the freezing cycle  20  (such as the compressor  22  and the valve  25 ) are controlled by a controller  29  provided to an electrical unit in the refrigerator  1 . 
     As illustrated in  FIG. 2 , the freezing cycle  20  has a first route including: the compressor  22 ; the condenser  23 ; the first capillary tube (expander)  24 ; and the freezer compartment evaporator (the first cooler)  21 . Moreover, the freezing cycle  20  has a second route including: the compressor  22 ; the condenser  23 ; the valve  25 ; the second capillary tube (the expander)  26 ; and the refrigerator compartment evaporator (the second cooler)  27 . The valve  25  is placed near a bifurcation of the first route and the second route. The valve  25  in this embodiment is a two-way valve. Alternatively, the valve  25  in other embodiments may be a three-way valve. 
     As illustrated in  FIG. 1 , the freezer compartment evaporator  21  is placed in a cooling room  15 . The cooling room  15  is placed in back of the freezer compartment  12  and provided along the back face  1   c  of the refrigerator  1 . The refrigerator compartment evaporator  27  is placed inside the refrigerator compartment  11 . In an example, the refrigerator compartment evaporator  27  is a cooling plate  127  attached to a wall face (e.g., a back face) of the refrigerator compartment  11 . The compressor  22  is placed inside a machine room  13  on the bottom of, and in the back of, the refrigerator  1 . 
     The cooling room  15  includes therein such components as a cooling fan  33 , other than the freezer compartment evaporator  21 . The cooling fan  33  is provided to circulate air between the cooling room  15  and the storage spaces. That is, operating in conjunction with the operation of the compressor  22 , the cooling fan  33  (i) sends, through flow passages to the storage spaces, the cooled air generated by heat exchange with the freezer compartment evaporator  21 , and (ii) brings the cooled air supplied to the storage spaces back to the cooling room  15 . 
     When the compressor  22  is driven, the freezing cycle  20  starts operating and the refrigerant flows in the direction indicated by arrows in  FIG. 2 . During the operation of the freezing cycle  20 , the refrigerant always flows through the first route. Meanwhile, the refrigerant flows through the second route when the valve  25  opens. 
     Compressed by the compressor  22 , the refrigerant has a high temperature and pressure. Releasing heat, the refrigerant is compressed in the condenser  23 , and then liquefied. The liquefied refrigerant passes through the first capillary tube  24  acting as an expander. After that, the refrigerant is sent to the freezer compartment evaporator  21  to expand to have a low temperature and pressure. The refrigerant flowing into the freezer compartment evaporator  21  exchanges heat with the air flowing through the cooling room  15 . Absorbing the heat and evaporating, the refrigerant becomes a gaseous refrigerant at a low temperature. Hence, the air inside the cooling room  15  is cooled to be the cooled air. The gaseous refrigerant; that is, the vaporized refrigerant in the freezer compartment evaporator  21 , is sent to the compressor  22 . 
     Moreover, when the valve  25  is open, the liquefied refrigerant is also sent to another expander; that is, the second capillary tube  26 . The liquefied refrigerant passes through the second capillary tube  26 . After that, the refrigerant is sent to the refrigerator compartment evaporator  27  to expand to have a low temperature and pressure. The refrigerant passing through the refrigerator compartment evaporator  27  expands to be vaporized. Here, the refrigerant absorbs heat from the surroundings such that the air inside the refrigerator compartment  11  provided with the refrigerator compartment evaporator  27  is cooled. The gaseous refrigerant; that is, the vaporized refrigerant in the refrigerator compartment evaporator  27 , is sent to the compressor  22 . 
     In the second route of the freezing cycle  20 , the valve  25  is opened and closed to control the circulation of the refrigerant. Hence, the opening and closing of the valve  25  is controlled based on a result of detecting the temperature inside the refrigerator compartment  11 , so that the temperature inside the refrigerator compartment  11  is adjusted to reach a desired temperature. 
     How to Cool Storage Spaces 
     Described next is how to cool the refrigerator compartment  11  and the freezer compartment  12 . 
     The refrigerator compartment  11  is cooled by the refrigerator compartment evaporator  27  provided in the second route of the freezing cycle  20 . Specifically, the refrigerator compartment  11  is cooled by the cooling plate  127  placed on the back face of the refrigerator compartment  11 . Note that a refrigerator compartment fan  142  is provided inside the refrigerator compartment  11  to stir the inside air. Moreover, a return opening  17  is provided inside the refrigerator compartment  11  to bring the inside air back to the cooling plate  127 . Hence, the air cooled near the cooling plate  127  circulates inside the refrigerator compartment  11 . In an example, the refrigerator compartment  11  is designed so that the inside thereof reaches a temperature of approximately 4° C. when the temperature inside the refrigerator compartment  11  is stable while the cooling plate  127  has a temperature of −1° C. and the refrigerator compartment fan  142  is rotating. Hence, the cooling plate  127  is provided inside, and cools, the storage space. Such a technique is referred to as the direct-cooling. 
     In addition to the cooling using the cooling plate  127 , the refrigerator compartment  11  is also cooled with the cooled air generated by the freezer compartment evaporator  21 . That is, the back face of the refrigerator compartment  11  is provided with a cooled air delivery passage  16  communicating with the cooling room  15 . Between the refrigerator compartment  15  and the cooled air delivery passage  16 , a refrigerator compartment delivery damper  141  is provided. If the temperature and the humidity inside the refrigerator compartment  11  satisfy a predetermined condition, for example, the refrigerator compartment delivery damper  141  is open so that the cooled air subjected to heat exchange by the freezer compartment evaporator  21  passes through the cooled air delivery passage  16  and flows it to the refrigerator compartment  11 . 
     Hence, the cooled air, subjected to heat exchange by the freezer compartment evaporator  21 , is delivered into, and cools, the storage space. Such a technique is referred to as the indirect-cooling. 
     The freezer compartment  12  is cooled only with the cooled air generated by the freezer compartment evaporator  21 . That the freezer compartment  12  communicates with the cooling room  15 . The cooled air subjected to heat exchange by the freezer compartment evaporator  21  is blown inside the freezer compartment  12 , using the cooling fan  33 , and the freezer compartment  12  is cooled. 
     As can be seen, in the refrigerator  1  according to this embodiment, the refrigerator compartment  11  is cooled by both the direct-cooling and the indirect-cooling. Note that the refrigerator compartment  11  is cooled mainly by the direct-cooling, and the indirect-cooling is used as necessary. The controller  29  controls the operation of the compressor  22 , the opening and closing of the valve  25 , and the opening and closing of the refrigerator compartment delivery damper  141 , based on, for example, conditions of a temperature and a humidity inside the refrigerator compartment  11  and the freezer compartment  12 . 
     In an example, based on a result of detecting a temperature of the freezer compartment  12 , the controller  29  controls ON/OFF of the compressor  22  in the freezing cycle  20 . For example, the controller  29  turns the compressor  22  ON when the temperature of the freezer compartment  12  rises higher than or equal to a predetermined value (e.g., −16° C.). Moreover, the controller  29  turns the compressor  22  OFF when the temperature of the freezer compartment  12  falls lower than or equal to a predetermined value (e.g., −22° C.). When the compressor  22  is ON, the refrigerant circulates in the freezing cycle  20  (at least in the first route). 
     Moreover, while the compressor  22  is running, the controller  29  controls the opening and closing of the valve  25  based on a result of detecting a temperature of the cooling plate  127  (alternatively, a temperature of the refrigerator compartment  11 ). For example, the controller  29  opens the valve  25  when the temperature of the cooling plate  127  rises higher than or equal to a predetermined value (e.g., 3° C.). Moreover, the controller  29  closes the valve  25  when the temperature of the cooling plate  127  falls lower than or equal to a predetermined value (e.g., −1° C.). When the valve  25  is open, the refrigerant circulates in the second route of the freezing cycle  20 , and the cooling plate  127  is cooled. 
     Furthermore, the controller  29  controls the opening and closing of the refrigerator compartment delivery damper  141 , based on a result of detecting a temperature and a humidity inside the refrigerator compartment  11 . For example, the controller  29  opens the refrigerator compartment delivery damper  141  when the humidity inside the refrigerator compartment  11  rises higher than or equal to a predetermined value. Moreover, the controller  29  closes the refrigerator compartment delivery damper  141  when the temperature or the humidity inside the refrigerator compartment  11  falls below the predetermined value. When the refrigerator compartment delivery damper  141  is open, the cooled air colder and less humid flows from the cooling room  15  into the refrigerator compartment  11 . Such features make it possible to decrease the temperature inside the refrigerator compartment  11  in a short period of time, and also decrease the humidity inside the refrigerator compartment  11 . Note that the level of the humidity inside the refrigerator compartment  11  may be determined based on a dew point inside the refrigerator compartment  11 . The dew point under a predetermined condition can be unambiguously calculated from a humidity and a temperature under the predetermined condition. 
     How to Control Temperature and Humidity of Refrigerator Compartment 
     Described next is how to control the temperature and the humidity of the refrigerator compartment  11 .  FIG. 3  illustrates a more specific configuration of the inside of the refrigerator compartment  11  of the refrigerator  1 . Furthermore,  FIG. 4  illustrates an example of how to control the temperature and the humidity inside the refrigerator compartment  11 . 
     As illustrated in  FIG. 3 , the inside of the refrigerator compartment  11  according to the first embodiment is divided by a divider shelf  155  into two spaces; namely, an upper space  118  and a lower space  119 . For example, the upper space  118  can be used as a typical refrigerator compartment, and the lower space  119  can be used for such compartments as a chilling compartment and a vegetable compartment. 
     The cooling plate  127  included in the second route of the freezing cycle  20  is placed on the wall face n back of the cooled air delivery passage  16  provided in the back of the refrigerator compartment  11 . The refrigerator compartment fan  142  is placed in an upper portion the refrigerator compartment  11  and between the cooled air delivery passage  16  and the upper space  118 . The operation of the refrigerator compartment fan  142  is controlled based on, for example, a condition of temperature inside the refrigerator compartment  11 . The arrangement of the cooling plate  127  and the refrigerator compartment fan  142  is not limited to such an arrangement. 
     Positioned near the cooling plate  127  (above the cooling plate  127  in the example s ted  FIG. 3 ) is a temperature-humidity sensor  143 . The position of the temperature-humidity sensor  143  is not limited to such a position. The temperature-humidity sensor  143  detects a temperature and a humidity near the cooling plate  127 . Note that, in this embodiment, the temperature and the humidity detected by the temperature-humidity sensor  143  are interpreted to be the temperature and the humidity inside the refrigerator compartment  11 . 
     A dew point inside the refrigerator compartment  11  is calculated, by a conventionally known technique, from the temperature and the humidity (relative humidity) measured by the temperature-humidity sensor  143 . Note that, in other embodiments, a temperature sensor and a dew point sensor can be used instead of the temperature-humidity sensor  143 . 
     In this embodiment, based on the temperature of the refrigerator compartment  11  measured by the temperature-humidity sensor  143  and the dew point calculated from the temperature and the humidity measured by the temperature-humidity sensor  143 , the opening and closing of the valve  25  in the freezing cycle  20  and the opening and closing of the refrigerator compartment delivery damper  141  are controlled. 
     A specific control technique is described with reference to  FIG. 4 . In an exemplary explanation in  FIG. 4 , the refrigerator compartment delivery damper  141  is initially closed, and the valve  25  is initially closed. 
     First, the controller  29  determines whether a calculated dew point is higher than or equal to a predetermined temperature (a first threshold) (Step S 11 ). If the dew point is lower than the first threshold (NO in Step S 11 ), the refrigerator compartment delivery damper  141  is kept closed, and the processing proceeds to Step S 15 . 
     Meanwhile, if the dew point is higher than or equal to the first threshold (YES in Step S 11 ), the refrigerator compartment delivery damper  141  is open (Step S 12 ). When the refrigerator compartment delivery damper  141  is open, colder cooled air (e.g., approximately −20 to −15° C.) generated in the cooling room  15  flows through the cooled air delivery passage  16  into the refrigerator compartment  11 . Hence, the temperature inside the refrigerator compartment  11  quickly falls. 
     Note that the low-temperature cooled air generated inside the cooling room  15  is low in water content, and drier than the air inside the refrigerator compartment  11 . That is, the cooled air generated inside the cooling room  15  is lower in humidity. Hence, when the refrigerator compartment delivery damper  141  is opened, the humidity inside the refrigerator compartment  11  decreases. Accordingly, the dew point decreases, too. 
     The controller  29  calculates the dew point inside the refrigerator compartment  11  from the temperature and the humidity measured by the temperature-humidity sensor  143  at all times or at regular time intervals. Then, the controller  29  determines whether the calculated dew point falls below a predetermined temperature (a second threshold) (Step S 13 ). If the dew point is higher than or equal to the second threshold (NO in Step S 13 ), the refrigerator compartment delivery damper  141  is kept open. 
     After that, if the dew point calculated from the temperature and the humidity measured by the temperature-humidity sensor  143  falls below the second threshold (YES in Step S 13 ), the controller  29  turns the refrigerator compartment delivery damper  141  from open to closed (Step S 14 ). 
     Then, the processing proceeds to Step S 15 . In the processing subsequent to Step S 15 , the controller  29  controls the opening and closing of the valve  25 , based on the temperature, inside the refrigerator compartment  11 , measured by the temperature-humidity sensor  143 . 
     In Step S 15 , the controller  29  determines whether the temperature inside the refrigerator compartment  11  is higher than or equal to a predetermined temperature (a third threshold) (Step S 15 ). If the temperature inside the refrigerator compartment  11  is lower than the third threshold (NO in Step S 15 ), the valve  25  is kept closed. Then, the controller  29  repeats the processing in Step S 15 . 
     Then, if the temperature inside the refrigerator compartment  11  rises higher than or equal to the third threshold, (YES in Step S 15 ), the controller  29  turns the valve  25  from closed to open (Step S 16 ). Hence, the refrigerant in the freezing cycle  20  circulates also in the second route, and the cooling plate  127  is cooled. As a result, the temperature inside the refrigerator compartment  11  gradually falls. 
     The controller  29  continues to monitor the temperature inside the refrigerator compartment  11 , and determines whether the temperature inside the refrigerator compartment  11  falls below a predetermined temperature (a fourth threshold) (Step S 17 ). If the temperature inside the refrigerator compartment  11  is higher than or equal to the fourth threshold (NO in Step S 17 ), the valve  25  is kept open. Then, the controller  29  repeats the processing in Step S 17 . 
     After that, if the temperature inside the refrigerator compartment  11  falls below the fourth threshold, (YES in Step S 17 ), the controller  29  turns the valve  25  from open to closed (Step S 18 ). The closed valve  25  stops the supply of the refrigerant to the second route in the freezing cycle  20 . Hence, the decrease in the temperature of the cooling plate  127  stops, and then, the temperature of the cooling plate  127  starts rising. 
     As can be seen, the controller  29  controls the opening and closing of the valve  25  in the freezing cycle  20 , and the opening and closing of the refrigerator compartment delivery damper  141 , thereby maintaining the temperature and the humidity inside the refrigerator compartment  11  in an appropriate condition. 
     In the above processing, the first threshold of the dew point is also referred to as a damper opening dew point. The damper opening dew point may be set to 1° C., for example. Moreover, the second threshold of the dew point is also referred to as a damper closing dew point. The damper closing dew point may be set to −1° C., for example. Furthermore, the third threshold of the temperature inside the refrigerator compartment is also referred to as a valve opening temperature. The valve opening temperature may be set to 3° C., for example. In addition, the fourth threshold of the temperature inside the refrigerator compartment is also referred to as a valve closing temperature. The valve closing temperature may be set to −1° C., for example. 
     Application to Vegetable Compartment 
     If the lower space  119  of the refrigerator compartment  11  is a vegetable compartment, described next is how to maintain the temperature and humidity inside the vegetable compartment in an appropriate condition, using the above control technique. 
     Desirably, vegetable are preserved under an environment at a relatively high humidity and at a low temperature which is not excessively low to keep from freezing. Moreover, it is known that leafy vegetables such as spinach and  komatsuna  (i.e., Japanese mustard spinach) stay fresh longer as the temperature is lower. Note that, however, if the vegetables get frozen or wet, the frozen or wet portion starts to go bad. Hence, the vegetables may be preserved in an environment which keeps them from freezing and condensation. 
     Thus, in the refrigerator compartment  11 , for example, the temperatures of the upper space  118  and the lower space  119  (i.e., the vegetable compartment) are respectively set to 4° C. and 0.5° C. Moreover, in order to maintain the humidity of the vegetable compartment in an appropriate condition, the above control technique is used to maintain the dew point inside the refrigerator compartment  11  within a desired temperature range. 
     Table 1 below shows relationships between humidities, temperatures, and dew points. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Humid- 
                 Temperature 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 ity 
                 0.0 
                 0.5 
                 1.0 
                 1.5 
                 2.0 
                 2.5 
                 3.0 
                 3.5 
                 4.0 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                  9% 
                 −27.8 
                 −27.5 
                 −27.1 
                 −26.8 
                 −26.4 
                 −26.1 
                 −25.7 
                 −25.4 
                 −25.0 
               
               
                 70% 
                 −4.8 
                 −4.3 
                 −3.9 
                 −3.4 
                 −2.9 
                 −2.4 
                 −2.0 
                 −1.5 
                 −1.0 
               
               
                 72% 
                 −4.4 
                 −3.9 
                 −3.4 
                 −2.9 
                 −2.4 
                 −2.0 
                 −1.5 
                 −1.0 
                 −0.5 
               
               
                 75% 
                 −3.9 
                 −3.4 
                 −2.9 
                 −2.4 
                 −2.0 
                 −1.5 
                 −1.0 
                 −0.5 
                 0.0 
               
               
                 78% 
                 −3.4 
                 −2.9 
                 −2.5 
                 −2.0 
                 −1.5 
                 −1.0 
                 −0.5 
                 0.0 
                 0.5 
               
               
                 80% 
                 −2.9 
                 −2.5 
                 −2.0 
                 −1.5 
                 −1.0 
                 −0.5 
                 0.0 
                 0.5 
                 0.9 
               
               
                 83% 
                 −2.5 
                 −2.0 
                 −1.5 
                 −1.0 
                 −0.5 
                 0.0 
                 0.5 
                 1.0 
                 1.4 
               
               
                 86% 
                 −2.0 
                 −1.5 
                 −1.0 
                 −0.5 
                 0.0 
                 0.5 
                 1.0 
                 1.5 
                 1.9 
               
               
                 90% 
                 −1.5 
                 −1.0 
                 −0.5 
                 0.0 
                 0.5 
                 1.0 
                 1.5 
                 2.0 
                 2.4 
               
               
                 93% 
                 −1.0 
                 −0.5 
                 0.0 
                 0.5 
                 1.0 
                 1.5 
                 2.0 
                 2.5 
                 3.0 
               
               
                 96% 
                 −0.5 
                 0.0 
                 0.5 
                 1.0 
                 1.5 
                 2.0 
                 2.5 
                 3.0 
                 3.5 
               
               
                 100%  
                 0.0 
                 0.5 
                 1.0 
                 1.5 
                 2.0 
                 2.5 
                 3.0 
                 3.5 
                 4.0 
               
               
                   
               
            
           
         
       
     
     In the above example, if the dew point is controlled to be set to −1° C. when the vegetable compartment has a set temperature of 0.5° C., the vegetable compartment (the lower space  119 ) has a humidity of 90%, making it possible to provide a condensation-free storage space at high humidity. Hence, in the above control technique, the damper opening dew point and the damper closing dew point are set so that a target value of the dew point in the refrigerator compartment  11  is −1° C. Hence, the temperature and the humidity of the vegetable compartment (the lower space  119 ) can be maintained in an appropriate condition. 
     Summary of First Embodiment 
     As can be seen, the refrigerator  1  according to this embodiment includes: the freezer compartment evaporator (the first cooler)  21 ; the refrigerator compartment  11 ; and the freezer compartment  12 . The refrigerator compartment  11  is cooled by direct-cooling, using the cooling plate  127 . The inside of the freezer compartment  12  is cooled by circulation of the cooled air subjected to heat exchange by the freezer compartment evaporator  21 . Moreover, the refrigerator  1  sends the refrigerator compartment  11  the cooled air subjected to heat exchange by the freezer compartment evaporator  21 . Specifically, when the refrigerator compartment delivery damper  141  is open, the cooled air inside the cooling room  15  can be sent from the cooled air delivery passage  16  into the refrigerator compartment  11 ; that is the refrigerator compartment  11  can be cooled by the indirect-cooling. 
     Because of this configuration, the refrigerator compartment  11  is cooled by the direct-cooling, so that the humidity inside the refrigerator compartment  11  can be maintained high. Moreover, if the refrigerator compartment  11  is to be quickly cooled, the refrigerator compartment delivery damper  141  is opened to send from the cooling room  15  the cooled air at lower temperature. Hence, the refrigerator compartment  11  can be quickly cooled. 
     Furthermore, the refrigerator  1  according to this embodiment executes the following control: if the dew point rises higher than or equal to a predetermined temperature (the first threshold), the refrigerator compartment delivery damper  141  is opened, and if the dew point falls below a predetermined temperature (the second threshold), the refrigerator compartment delivery damper  141  is closed. This control can reduce the risk that the humidity inside the refrigerator compartment  11  rises excessively high while the temperature inside the refrigerator compartment  11  is relatively high. Such a feature makes it possible to reduce formation of condensation inside the refrigerator compartment  11 . Note that the temperature of the cooling plate  127  is maintained above the dew point, making it possible to further reduce formation of condensation on the cooling plate  127 . 
     Note that, in the above embodiment, the refrigerator compartment delivery damper  141  is opened and closed to control flow of the cooled air inside the cooling room  15  into the refrigerator compartment  11 . Alternatively, in other embodiments, an air volume of the fan, instead of the damper, may be adjusted to control the cooled air to be sent to the refrigerator compartment. 
     Second Embodiment 
     Described next is a second embodiment of the present invention. The second embodiment is different in position of a temperature-humidity sensor from the first embodiment. Otherwise, configurations similar to those in the first embodiment may be applicable. Hence, the second embodiment mainly describes configurations different from those in the first embodiment. 
       FIG. 5  illustrates an internal configuration of a refrigerator  201  according to the second embodiment. The inside of the refrigerator compartment  11  is divided by the divider shelf  155  into two spaces; namely, the upper space  118  and the lower space  119 . The cooled air delivery passage  16  is provided in the back of the refrigerator compartment  11 , The cooling plate  127  is provided on the wall face in back of the cooled air delivery passage  16 . Between the cooled air delivery passage  16  and the upper space  118 , the refrigerator compartment fan  142  is provided. These configurations are the same as those in the first embodiment. 
     The refrigerator compartment  11  includes therein a temperature-humidity sensor  243  and a cooling plate temperature sensor  244 . In the first embodiment, the temperature-humidity sensor  143  is placed near the cooling plate  127 . In contrast, the temperature-humidity sensor  243  in this embodiment is placed on a top face of the refrigerator compartment near the refrigerator compartment door  11   a  near an access opening of the refrigerator compartment  11 ). Furthermore, in this embodiment, the cooling plate temperature sensor  244 , which is another temperature sensor, is placed near the cooling plate  127 . Note that in another embodiment, a sensor placed near the cooling plate  127  may be a temperature-humidity sensor, and a sensor placed near the refrigerator compartment door  11   a  may be a temperature sensor. 
     A temperature and a humidity inside the refrigerator compartment  11  detected by the temperature-humidity sensor  243  is mainly used for controlling opening and closing of the refrigerator compartment delivery damper  141 . Moreover, a temperature of the cooling plate  127  detected by the cooling plate temperature sensor  244  is mainly used for controlling opening and closing of the valve  25 . 
     Described below is an example of how to control the temperature and the humidity of the refrigerator compartment  11  with reference to  FIG. 6 . Moreover,  FIG. 6  shows an example of how to control the temperature and the humidity inside the refrigerator compartment  11 . In the exemplary explanation in  FIG. 6 , the refrigerator compartment delivery damper  141  is initially closed and the valve  25  is initially closed. 
     First, the controller  29  determines whether a condition to open the refrigerator compartment delivery damper  141  (a damper opening condition) is satisfied (Step S 21 ). Here, the damper opening condition is satisfied if either condition; namely a condition (A) or a condition (B), is satisfied (an OR condition). 
     (A) The dew point calculated from the temperature and the humidity detected by the temperature-humidity sensor  243  is higher than or equal to a predetermined temperature (a first threshold); that is, the dew point≥the first threshold. 
     (B) The temperature detected by the temperature-humidity sensor  243  is higher than or equal to a predetermined temperature (a second threshold); that is, the temperature inside the refrigerator compartment≥the second threshold. 
     Note that, in order to keep the inside of the refrigerator compartment  11  from excessively cooling, the damper opening condition may include a precondition; that is, if the temperature inside the refrigerator compartment is lower than a predetermined temperature, the refrigerator compartment delivery damper  141  is not opened. 
     In Step S 21 , if the damper opening condition is not satisfied (NO in Step S 21 ), the refrigerator compartment delivery damper  141  is kept closed. The processing proceeds to Step S 25 . 
     Meanwhile, if the damper opening condition is satisfied (YES in Step S 21 ), the refrigerator compartment delivery damper  141  is opened (Step S 22 ). When the refrigerator compartment delivery damper  141  is opened, the cooled air generated inside the cooling room  15  flows through the cooled air delivery passage  16  into the refrigerator compartment  11 . Hence, the temperature inside the refrigerator compartment  11  quickly falls. 
     Note that the cooled air generated inside the cooling room  15  is low in water content, and drier than the air inside the refrigerator compartment  11 . That is, the cooled air ted inside the cooling room  15  is lower in humidity. Hence, when the refrigerator compartment delivery damper  141  is opened, the humidity inside the refrigerator compartment  11  decreases. Accordingly the dew point decreases, too. 
     The controller  29  calculates the dew point inside the refrigerator compartment  11  from the temperature and the humidity measured by the temperature-humidity sensor  243  at all times or at regular time intervals. Then, the controller  29  determines whether a condition to close the refrigerator compartment delivery damper  141  (a damper closing condition) is satisfied (Step S 23 ). Here, the damper closing condition is satisfied if both of the conditions; namely a condition (C) and a condition (D), are satisfied (an AND condition). 
     (C) The dew point calculated from the temperature and the humidity detected by the temperature-humidity sensor  243  is lower than a predetermined temperature (a third threshold); that is, the dew point&lt;the first threshold. 
     (D) The temperature detected by the temperature-humidity sensor  243  is lower than a predetermined temperature (a fourth threshold); that is, the temperature inside the refrigerator compartment&lt;the fourth threshold. 
     Note that, in order to keep the inside of the refrigerator compartment  11  from excessively cooling, the damper closing condition may include a precondition; that is, if the temperature inside the refrigerator compartment is lower than a predetermined temperature, the refrigerator compartment delivery damper  141  is closed Moreover, in another embodiment, the damper closing condition may be satisfied if either the condition (C) or the condition (D) is satisfied (an OR condition). 
     In Step S 23 , if the damper closing condition is not satisfied (NO in Step S 23 ), the refrigerator compartment delivery damper  141  is kept open. 
     After that, if the damper closing condition is satisfied (YES in Step S 23 ), the controller  29  turns the refrigerator compartment delivery damper  141  from open to closed (Step S 24 ). 
     Then, the processing proceeds to Step S 25 . In the processing subsequent to Step S 25 , the controller  29  controls the opening and closing of the valve  25 , based on the temperature measured by the temperature-humidity sensor  244 . 
     In Step S 25 , the controller  29  determines whether the temperature of the cooling plate  127  is higher than or equal to a predetermined temperature (a fifth threshold) (Step S 25 ). If the temperature of the cooling plate  127  is lower than the fifth threshold (NO in Step S 25 ), the valve  25  is kept closed. Then, the controller  29  repeats the processing in Step S 25 . 
     Then, if the temperature inside the refrigerator compartment  11  rises higher than or equal to the fifth threshold, (YES in Step S 25 ), the controller  29  turns the valve  25  from closed to open (Step S 26 ). Hence, the refrigerant in the freezing cycle  20  circulates also in the second route, and the cooling plate  127  is cooled. As a result, the temperature inside the refrigerator compartment  11  gradually falls. 
     The controller  29  continues to monitor the temperature inside the refrigerator compartment  11 , and determines whether the temperature inside the refrigerator compartment  11  falls below a predetermined temperature (a sixth threshold) (Step S 27 ). If the temperature inside the refrigerator compartment  11  is higher than or equal to the sixth threshold (NO in Step S 27 ), the valve  25  is kept open. Then, the controller  29  repeats the processing in Step S 27 . 
     After that, if the temperature inside the refrigerator compartment  11  falls below the sixth threshold, (YES in Step S 27 ), the controller  29  turns the valve  25  from open to closed (Step S 28 ). The closed valve  25  stops the supply of the refrigerant to the second route in the freezing cycle  20 . Hence, the decrease in the temperature of the cooling plate  127  stops, and then, the temperature of the cooling plate  127  starts rising. 
     As can be seen, the controller  29  controls the opening and closing of the valve  25  in the freezing cycle  20  and of the refrigerator compartment delivery damper  141 , thereby maintaining the temperature and the humidity inside the refrigerator compartment  11  in an appropriate condition. 
     In the above processing, the first threshold of the dew point is also referred to as a damper opening dew point. The damper opening dew point may be set to 1° C., for example. Moreover, the second threshold of the temperature inside the refrigerator compartment is also referred to as a damper opening refrigerator compartment temperature. The damper opening refrigerator compartment temperature may be set to 7° C., for example. Furthermore, the third threshold of the dew point is also referred to as a damper closing dew point. The damper closing dew point may be set to −1° C., for example. In addition, the fourth threshold of the temperature inside the refrigerator compartment is also referred to as a damper closing refrigerator compartment temperature. The damper closing refrigerator compartment temperature may be set to 1° C., for example. In addition, the fifth threshold of the temperature of the cooling plate is also referred to as a valve opening temperature. The valve opening temperature may be set to 3° C., for example. Furthermore, the sixth threshold of the temperature of the cooling plate is also referred to as a valve closing temperature. The valve closing temperature may be set to −1° C., for example. 
     As can be seen, the temperature-humidity sensor  243  in this embodiment is placed on the top face of the refrigerator compartment near the refrigerator compartment door  11   a  near the access opening of the refrigerator compartment  11 ). Near the access opening of the refrigerator compartment  11 , the temperature-humidity sensor  243  is susceptible to the outside air because of the opening and closing of the refrigerator compartment door  11   a . Hence, the temperature detected by the temperature-humidity sensor  243  is likely to rise higher than the temperature detected near the cooling plate  127 . 
     If the refrigerator compartment door  11   a  is frequently opened and closed, and a warm meal is put in the refrigerator compartment  11 , the temperature might differ between the refrigerator compartment  11  and the cooling plate  127 . In such a case, as shown in this embodiment, the opening and closing of the refrigerator compartment delivery damper  141  is controlled based on the temperature and the humidity measured by the temperature-humidity sensor  243  provided near the refrigerator compartment door  11   a , making it possible to cool the refrigerator compartment more quickly. 
     Third Embodiment 
     Described next is a third embodiment of the present invention. The third embodiment is different in arrangement of a cooling plate and a temperature-humidity sensor from the first embodiment. Otherwise, configurations similar to those in the first embodiment may be applicable. Hence, the third embodiment mainly describes configurations different from those in the first embodiment. 
       FIG. 7  illustrates an internal configuration of a refrigerator  301  according to the third embodiment. The inside of the refrigerator compartment  11  is divided by a divider shelf  355  into two spaces; namely, the upper space  118  and the lower space  119 . The cooled air delivery passage  16  is provided in the back of the refrigerator compartment  11 . As to these features, configurations substantially similar to those in the first embodiment may be applicable. 
     In this embodiment, the position of the cooling plate  327  is different from that of the cooling plate  127  in the first embodiment. In this embodiment, the cooling plate  327  is provided in the lower space  119 . The temperature set in the lower space  119  is lower than the temperature set in the upper space  118 . The lower space  119  and the upper space  118  are also respectively referred to as a low-temperature room and a high-temperature room. Since the cooling plate  327  is provided in the low-temperature room whose temperature is set lower, the low-temperature room can be preferentially cooled. 
     The lower space  119  can be used for a vegetable compartment and a chilling compartment, for example. Moreover, the lower space  119  can be maintained in a condition at a relatively high humidity and at a low-temperature which is not excessively low to keep from freezing. Hence, the lower space  119  can be beneficially used as a vegetable compartment. 
     Furthermore, as illustrated in  FIG. 7 , a refrigerator compartment interior circulation route  356  is formed in back of the divider shelf  355 . Then, provided above the refrigerator compartment interior circulation route  356  is the refrigerator compartment fan  142 . When the refrigerator compartment fan  142  rotates, the air can circulate between the upper space  118 , the lower space  119 , and the refrigerator compartment interior circulation route  356 . 
     Provided below the refrigerator compartment interior circulation route  356  (i.e., in the back of the lower space  119 ) is a temperature-humidity sensor  343 . Hence, preferably, the temperature-humidity sensor  343  is slightly apart from the cooling plate  327 , and positioned to be able to detect the temperature of the air stirred by the refrigerator compartment fan  142  and then passing near the cooling plate  327 . An example of such a position includes the inside or the neighborhood of the low-temperature room. Since the temperature-humidity sensor  343  is provided in such a position, the two temperature sensors (i.e., the temperature-humidity sensor  243  and the cooling plate temperature sensor  244 ) described, for example, in the second embodiment can be combined into one temperature sensor. 
     Described below is an example of how to control the temperature and the humidity of the refrigerator compartment  11  with reference to  FIG. 8 . Moreover,  FIG. 8  shows an example of how to control the temperature and the humidity inside the refrigerator compartment  11 . In the exemplary explanation in  FIG. 8 , the r e for compartment delivery damper  141  is initially closed and the valve  25  is initially closed. 
     First, the controller  29  determines whether a condition to open the refrigerator compartment delivery damper  141  (a damper opening condition) is satisfied (Step S 31 ). Here, as seen in the second embodiment, the damper opening condition is satisfied if either condition; namely the condition (A) or the condition (B) described above, is satisfied (an OR condition). 
     In Step S 31 , if the damper opening condition is not satisfied (NO in Step S 31 ), the refrigerator compartment delivery damper  141  is kept closed. The processing proceeds to Step S 35 . 
     Meanwhile, if the damper opening condition is satisfied (YES in Step S 31 ), the refrigerator compartment delivery damper  141  is opened (Step S 32 ). When the refrigerator compartment delivery damper  141  is opened, the cooled air generated inside the cooling room  15  flows through the cooled air delivery passage  16  into the refrigerator compartment  11 . Hence, the temperature inside the refrigerator compartment  11  quickly falls. 
     Then, the controller  29  determines whether a condition to close the refrigerator compartment delivery damper  141  (a damper closing condition) is satisfied (Step S 33 ). Here, as seen in the second embodiment, the damper closing condition is satisfied if both of the conditions; namely the condition (C) and the condition (D) described above, are satisfied (an AND condition). Moreover, in another embodiment, the damper closing condition may be satisfied if either the condition (C) or the condition (D) is satisfied (are OR condition). 
     In Step S 33 , if the damper closing condition is not satisfied (NO in Step S 33 ), the refrigerator compartment delivery damper  141  is kept open. 
     After that, if the damper closing condition is satisfied (YES in Step S 33 ), the controller  29  turns the refrigerator compartment delivery damper  141  from open to closed (Step S 34 ). 
     Then, the processing proceeds to Step S 35 . In the processing subsequent to Step S 35 , the controller  29  controls the opening and closing of the valve  25 , based on the temperature measured by the temperature-humidity sensor  343 . 
     In Step S 35 , the controller  29  determines whether the temperature inside the refrigerator compartment  11  is higher than or equal to a predetermined temperature (a fifth threshold) (Step S 35 ). If the temperature of the refrigerator compartment  11  is lower than the fifth threshold (NO in Step S 35 ), the valve  25  is kept closed. Then, the controller  29  repeats the processing in Step S 35 . 
     Then, if the temperature inside the refrigerator compartment  11  rises higher than or equal to the fifth threshold, (YES in Step S 35 ), the controller  29  turns the valve  25  from closed to open (Step S 36 ). Hence, the refrigerant in the freezing cycle  20  circulates also in the second route, and the cooling plate  327  is cooled. As a result, the temperature inside the refrigerator compartment  11  gradually falls. 
     The controller  29  continues to monitor the temperature inside the refrigerator compartment  11 , and determines whether the temperature inside the refrigerator compartment  11  falls below a predetermined temperature (a sixth threshold) (Step S 37 ). If the temperature inside the refrigerator compartment  11  is higher than or equal to the sixth threshold (NO in Step S 37 ), the valve  25  is kept open. Then, the controller  29  repeats the processing in Step S 37 . 
     After that, if the temperature inside the refrigerator compartment  11  falls below the sixth threshold, (YES in Step S 37 ), the controller  29  turns the valve  25  from open to closed (Step S 38 ). The closed valve  25  stops the supply of the refrigerant to the second route in the freezing cycle  20 . Hence, the decrease in the temperature of the cooling plate  327  stops, and then, the temperature of the cooling plate  327  starts rising. 
     As can be seen, the controller  29  controls the opening and closing of the valve  25  in the freezing cycle  20  and of the refrigerator compartment delivery damper  141 , thereby maintaining the temperature and the humidity inside the refrigerator compartment  11  in an appropriate condition. 
     In the above processing, the first threshold of the dew point is also referred to as a damper opening dew point. The damper opening dew point may be set to 1° C., for example. Moreover, the second threshold of the temperature inside the refrigerator compartment is also referred to as a damper opening refrigerator compartment temperature. The damper opening refrigerator compartment temperature may be set to 11° C., for example. Furthermore, the third threshold of the dew point is also referred to as a damper closing dew point. The damper closing dew point may be set to −1° C., for example. In addition, the fourth threshold of the temperature inside the refrigerator compartment is also referred to as a damper closing refrigerator compartment temperature. The damper closing refrigerator compartment temperature may be set to 7° C., for example. Furthermore, the fifth threshold of the temperature inside the refrigerator compartment is also referred to as a valve opening temperature. The valve opening temperature may be set to 5° C., for example. In addition, the sixth threshold of the temperature inside the refrigerator compartment is also referred to as a valve closing temperature. The valve closing temperature may be set to 2° C., for example. 
     In this embodiment, the opening and closing of the valve  25  is controlled based on the temperature measured inside the refrigerator compartment  11  by the temperature-humidity sensor  343 . Thus, compared with the second embodiment in which the temperature of the cooling plate  127  is detected, the valve opening temperature and the valve closing temperature may be set relatively high. Moreover, the damper opening dew point is desirably lower than the valve closing temperature (or the lowermost temperature of the cooling plate  127 ). Hence, the inside of the refrigerator compartment  11  is cooled by the cooling plate  327  whenever possible. When the humidity, and then the dew point, inside the refrigerator compartment  11  rise, the dew point is decreased by the cooled air inside the cooling room  15 . Such a feature reduces the risk that the cooled air at low humidity inside the cooling room  15  excessively flows into the refrigerator compartment  11 , making it possible to keep the inside of the refrigerator compartment  11  from drying. 
       FIG. 9  illustrates an example of changes in temperature of compartments and a cooling plate and in dew point of the refrigerator compartment  11 , when the opening and closing of the refrigerator compartment delivery damper  141  and the valve  25 , and ON and OFF of the operation of the compressor  22  are controlled, using the above control technique. In  FIG. 9 , the reference sign A denotes a temperature of the refrigerator compartment  11  (i.e., a temperature measured by the temperature-humidity sensor  343 ), the reference sign B denotes a temperature of the cooling plate  327 , the reference sign C denotes a dew point of the refrigerator compartment  11  (i.e., a dew point calculated from the temperature and the humidity measured by the temperature-humidity sensor  343 ), and the reference sign D denotes a temperature of the freezer compartment  12 . Moreover, the reference sign E denotes opening and closing of the valve  25 , the reference sign F denotes opening and closing of the refrigerator compartment delivery damper  141 , and the reference sign G denotes an operation state of the compressor  22 . 
     In  FIG. 9 , time points ( 1 ), ( 3 ), and ( 5 ) are an example when to open the refrigerator compartment delivery damper  141  (i.e., time points when to send, to the refrigerator compartment  11 , the cooled air subjected to heat exchange by the freezer compartment evaporator  21 ). As illustrated in the graph of  FIG. 9 , the refrigerator compartment delivery damper  141  is turned from closed to open when the dew point reaches a predetermined temperature (1° C., for example). 
     In  FIG. 9 , time points ( 2 ), ( 4 ), and ( 6 ) are an example when to close the refrigerator compartment delivery damper  141  (i.e., time points when to stop the flow of the cooled air, subjected to heat exchange by the freezer compartment evaporator  21 , to the refrigerator compartment  11 ). As illustrated in the graph of  FIG. 9 , the refrigerator compartment delivery damper  141  is turned from open to closed when the temperature and the humidity of the refrigerator compartment  11  falls below predetermined values (i.e., when the above conditions (C) and (D) are satisfied). 
     As seen in this embodiment, the temperature-humidity sensor  343  is positioned in the lower space  119  (or, near the lower space  119 ) whose temperature is set lower. In this position, the temperature-humidity sensor  343  can accurately detect the temperature and the humidity of the lower space  119 . Thus, the lower space  119  can be maintained a condition at a relatively high humidity and at a low temperature which is not excessively low to keep from freezing. Hence, the lower space  119  can be beneficially used as a space to preserve vegetables. Moreover, in the refrigerator compartment  11 , the lower space  119  is set to have a low temperature and a high humidity. Such a feature makes it possible to control the opening and closing of the refrigerator compartment delivery damper  141  and of the valve  25 , based on the temperature detected by one temperature sensor provided in (or near) the lower space  119 . Note that the configuration in which the temperature-humidity sensor  343  is placed in the position illustrated in  FIG. 7  is an example of a configuration in which a temperature-humidity sensor is placed in a low-temperature room. 
     Moreover, when the temperature and the humidity of the refrigerator compartment  11  are controlled, as illustrated in  FIG. 9 , the temperature (B) of the cooling plate  327  is preferably maintained higher than the dew point (C) of the refrigerator compartment  11 . Such a feature makes it possible to minimize condensation formed on the cooling plate  327 . Hence, produce to be stored in the lower space  119  such as vegetables is kept from dew, such that the vegetables are likely to be kept fresh. 
     Fourth Embodiment 
     Described next is a fourth embodiment of the present invention. The above embodiments describe a configuration which involves cooling the refrigerator compartment  11  by the direct-cooling, using a cooling plate cooled by the second cooler (the refrigerator compartment evaporator) provided in the second route of the freezing cycle  20 . However, the technique to cool the refrigerator compartment using the direct-cooling shall not be limited to such a configuration. The fourth embodiment describes an example of a configuration which involves transmitting the cooled air inside the freezer compartment to a division wall between the refrigerator compartment and the freezer compartment, and using the division wall as a cooling plate. 
       FIG. 10  illustrates an internal configuration of a refrigerator  401  according to the fourth embodiment. The refrigerator compartment  11  and the freezer compartment  12  are divided by a division wall  452 . In the first embodiment, the refrigerator compartment  11  and the freezer compartment  12  are separated by the thermal insulation division wall  52  with high thermal insulation. Hence, not much cooled air is transmitted from the freezer compartment  12  through the thermal insulation division wall  52  to the refrigerator compartment  11 . In contrast, the refrigerator compartment  11  and the freezer compartment  12  in this embodiment are divided by a division wall  452  lower in thermal insulation than the thermal insulation division wall  52 . 
     Such a configuration makes it possible to transmit the cooled air inside the freezer compartment  12  to the refrigerator compartment  11 , and cool the inside of the refrigerator compartment  11 . That is, the division wall  452  acts as a cooling plate for cooling the inside of the refrigerator compartment  11  by the direct-cooling. Adoption of the direct-cooling in such a configuration eliminates the need of the second route in the freezing cycle  20 , making it possible to simplify the configuration of the freezing cycle  20 . 
     Note that if the cooled air inside the freezer compartment  12  is directly transmitted to the refrigerator compartment  11 , the inside of the refrigerator compartment  11  might be excessively cooled. Hence, a temperature compensation heater  428  is provided to a face in the division wall  452  toward the refrigerator compartment  11 . The temperature compensation heater  428  provided can maintain a surface of the division wall  452 , positioned toward the refrigerator compartment  11 , to have an appropriate temperature. 
     The refrigerator compartment  11  includes therein the temperature-humidity sensor  243  and a second temperature sensor  444 . As seen in the second embodiment, the temperature-humidity sensor  243  is placed on the top face of the refrigerator compartment near the refrigerator compartment door  11   a  (i.e., near the access opening of the refrigerator compartment  11 ). Moreover, the second temperature sensor  444  is placed near the division wall  452  and the temperature compensation heater  428 . 
     A temperature and a humidity inside the refrigerator compartment  11  detected by the temperature-humidity sensor  243  is mainly used for controlling opening and closing of the refrigerator compartment delivery damper  141 . Moreover, a temperature detected by the second temperature sensor  444  is mainly used for turning ON and OFF the temperature compensation heater  428 . 
     Described below is an example of how to control the temperature and the humidity of the refrigerator compartment  11  with reference to  FIG. 11 . Moreover,  FIG. 11  shows an example of how to control the temperature and the humidity inside the refrigerator compartment  11 . In the exemplary explanation in  FIG. 11 , the refrigerator compartment delivery damper  141  is initially closed and the temperature compensation heater  428  is initially OFF. 
     First, the controller  29  determines whether a condition to open the refrigerator compartment delivery damper  141  (a damper opening condition) is satisfied (Step S 41 ). Here, as seen in the second embodiment, the damper opening condition is satisfied if either condition; namely the condition (A) or the condition described above, is satisfied (an OR condition). 
     In Step S 41 , if the damper opening condition is not satisfied (NO in Step S 41 ), the refrigerator compartment delivery damper  141  is kept closed. The processing proceeds to Step S 45 . 
     Meanwhile, if the damper opening condition is satisfied (YES in Step S 41 ), the refrigerator compartment delivery damper  141  is opened (Step S 42 ). When the refrigerator compartment delivery damper  141  is opened, the cooled air generated inside the cooling room  15  flows through the cooled air delivery passage  16  into the refrigerator compartment  11 . Hence, the temperature inside the refrigerator compartment  11  quickly falls. 
     Then, the controller  29  determines whether a condition to close the refrigerator compartment delivery damper  141  (a damper closing condition) is satisfied (Step S 43 ). Here, as seen in the second embodiment, the damper closing condition is satisfied if both of the conditions; namely the condition (C) and the condition (D) described above, are satisfied (an AND condition). Note that, in another embodiment, the damper closing condition may be satisfied if either the condition (C) or the condition (D) is satisfied (an OR condition). 
     In Step S 43 , if the damper closing condition is not satisfied (NO in Step S 43 ), the refrigerator compartment delivery damper  141  is kept open. 
     After that, if the damper closing condition is satisfied (YES in Step S 43 ), the controller  29  turns the refrigerator compartment delivery damper  141  from open to closed (Step S 44 ). 
     Then, the processing proceeds to Step S 45 . In the processing subsequent to Step S 45 , the controller  29  controls ON and OFF of the temperature compensation heater  428 , based on the temperature measured by the second temperature sensor  444 . 
     In Step S 45 , the controller  29  determines whether the temperature of the division wall  452  measured by the second temperature sensor  444  is lower than a predetermined temperature (a fifth threshold) (Step S 45 ). If the temperature of the refrigerator compartment  11  is higher than or equal to the fifth threshold (NO in Step S 45 ), the temperature compensation heater  428  is kept OFF. Then, the controller  29  repeats the processing in Step S 45 . 
     After that, if the temperature of the division wall  452  falls below the fifth threshold, (YES in Step S 45 ), the controller  29  turns the temperature compensation heater  428  ON (Step S 46 ). Hence, the heat of the temperature compensation heater  428  warms the surface of the division wall  452  facing the refrigerator compartment  11 . Hence, the temperature inside the refrigerator compartment  11  gradually rises. 
     The controller  29  continues to monitor the temperature measured by the second temperature sensor  444 , and determines whether the temperature inside the refrigerator compartment  11  rises higher than or equal to a predetermined temperature (a sixth threshold) (Step S 47 ). If the temperature inside the refrigerator compartment  11  is lower than the sixth threshold (NO in Step S 47 ), the temperature compensation heater  428  is kept ON. Then, the controller  29  repeats the processing in Step S 47 . 
     Then, if the temperature inside the refrigerator compartment  11  rises higher than or equal to the sixth threshold, (YES in Step S 47 ), the controller  29  turns the temperature compensation heater  428  from ON to OFF (Step S 48 ). Hence, the temperature rise of the division wall  452  stops. As a result, an excessive temperature rise inside the refrigerator compartment  11  is curbed, maintaining the temperature inside the refrigerator compartment  11  in an appropriate condition. 
     As can be seen, the controller  29  controls ON and OFF of the temperature compensation heater  428  and the opening and closing of the refrigerator compartment delivery damper  141 , thereby maintaining the temperature and the humidity inside the refrigerator compartment  11  in an appropriate condition. 
     In the above processing, the first threshold of the dew point is also referred to as a damper opening dew point. The damper opening dew point may be set to 1° C., for example. Moreover, the second threshold of the temperature inside the refrigerator compartment is also referred to as a damper opening refrigerator compartment temperature. The damper opening refrigerator compartment temperature may be set to 7° C., for example. Furthermore, the third threshold of the dew point is also referred to as a damper closing dew point. The damper closing dew point may be set to −1° C., for example. In addition, the fourth threshold of the temperature inside the refrigerator compartment is also referred to as a damper closing refrigerator compartment temperature. The damper closing refrigerator compartment temperature may be set to 1° C., for example. In addition, the fifth threshold of the temperature of the division wall is also referred to as a heater ON temperature. The heater ON temperature may be set to −1° C., for example. In addition, the sixth threshold of the temperature of the division wall is also referred to as a heater OFF temperature. The heater OFF temperature may be set to 3° C., for example. 
     As can be seen, in the refrigerator compartment  401  according to this embodiment, the refrigerator compartment  11  and the freezer compartment  12  are divided by the division wall  452  lower in thermal insulation than the thermal insulation division wall  52 . This configuration makes it possible to transmit the cooled air inside the freezer compartment  12  to the refrigerator compartment  11 , and cool the inside of the refrigerator compartment  11 . Such a feature eliminates the need of the second route of the freezing cycle  20  for cooling the cooling plate, making it possible to simplify the configuration of the freezing cycle  20 . 
     Hence, the temperature compensation heater  428  is used to adjust the temperature of the surface of the division wall  452  acting as a cooling plate to cool the inside of the refrigerator compartment  11 . As a result, the inside of the refrigerator compartment  11  can be maintained to have an appropriate temperature. 
     While there have been described what are at present considered to be certain embodiments of the invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claim cover all such modifications as fall within the true spirit and scope of the invention.