Patent Publication Number: US-7908876-B2

Title: Refrigerator and method to control the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2007-0034406, filed on Apr. 6, 2007 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     The present invention relates to a refrigerator, and more particularly, to a refrigerator which can stably keep beverages in a supercooled state and a method to control the same. 
     2. Description of the Related Art 
     A refrigerator is generally a device that supplies cool air generated by a cooling unit to a storage compartment to maintain the freshness of various foods for a long time. If the inner temperature of the storage compartment of the refrigerator is controlled appropriately, it is possible to keep beverages in a supercooled state. By keeping beverages in the supercooled state, users can obtain beverages that are neither completely frozen nor completely melted, referred to as “slush”. 
     When the temperature of a beverage is reduced below the freezing point at 1 atmosphere, its phase generally changes from liquid to solid but, in some cases, it may be in a supercooled state without being changed to solid. The state of liquid in a supercooled state without freezing below the freezing point is thermodynamically referred to as a metastable state. In the metastable state, the supercooled liquid is neither completely unstable nor completely stable so that it instantly undergoes a phase change to solid upon receiving disturbance, such as impact or vibration from ambient environments. Thus, the user can obtain slush from a beverage by cooling the beverage below the freezing point in a refrigerator without allowing any disturbance to be applied, and then removing the beverage from the refrigerator and applying disturbance at a desired time. 
     To keep a beverage in a refrigerator in a supercooled state, it is necessary to cool the beverage below the freezing point. The supercooled level of the beverage increases as the inner temperature of the refrigerator decreases. However, if the inner temperature is too low, the supercooled state is broken to allow the beverage to freeze, thereby failing to obtain slush. The limit of the supercool temperature of commercial beverages generally ranges from about −8° C. to about −12° C., although this value varies slightly depending on the type of beverage. Thus, it is possible to keep beverages in a supercooled state by adjusting the refrigerator temperature in a range of temperatures slightly higher than the supercool temperature limit. 
     An example of a cooling device which can supercool beverages is described in Japanese Patent Application Publication No. 2003-214753 (entitled “COOLING DEVICE TO SUPERCOOL BEVERAGE” and published on Jun. 30, 2003). The cooling device of this publication supplies appropriate cool air to a storage compartment, in which beverages are stored, to keep the temperature of the storage compartment below the freezing point. 
     However, the conventional cooling device collectively adjusts the inner temperature of the refrigerator regardless of the types of beverages so that beverages with a relatively high freezing point may freeze while the supercooled level of beverages with a relatively low freezing point may be reduced. 
     Further, the probability that the beverages will freeze near the lowest temperature point is increased if the adjusted inner temperature of the refrigerator greatly varies. Thus, the inner temperature of the refrigerator must be adjusted with a variation less than a specific temperature level (for example, ±0.5° C.). However, it is very difficult to satisfy this requirement through the method of supplying cool air using the conventional cooling device. 
     SUMMARY 
     Therefore, it is an aspect of the present invention to provide a refrigerator and a method to control the same, which can stably keep beverages in the refrigerator in a supercooled state. 
     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention. 
     The foregoing and/or other aspects of the present invention may be achieved by providing a refrigerator including a body defining a supercooling compartment; a cooling unit to provide cool air to the supercooling compartment; an electromagnetic radiation sensor to detect electromagnetic radiation emitted when a food placed in the supercooling compartment begins to freeze; an energy supply to apply energy to the food placed in the supercooling compartment to prevent freezing of the food; and a controller to receive a detection signal from the electromagnetic radiation sensor and then to activate the energy supply. 
     A receiving portion where the food is to be placed may be provided in the supercooling compartment and the electromagnetic radiation sensor may be provided near the receiving portion. 
     A plurality of receiving portions may be provided and a plurality of electromagnetic radiation sensors corresponding respectively to the plurality of receiving portions may be provided. 
     A receiving portion where the food is to be placed may be provided in the supercooling compartment and the energy supply may be provided near the receiving portion. 
     A plurality of receiving portions may be provided and a plurality of energy supplies corresponding respectively to the plurality of receiving portions may be provided. 
     The controller may activate the energy supply when the electromagnetic radiation sensor detects electromagnetic radiation emitted when an ice nucleus forms in the food. 
     The controller may activate the energy supply when the electromagnetic radiation sensor detects electromagnetic radiation emitted when an ice nucleus grows in the food. 
     The refrigerator may further include a signal amplifier to amplify a detection signal generated by the electromagnetic radiation sensor. 
     The energy supply may be an electric heater capable of heating the food. 
     The foregoing and/or other aspects of the present invention may also be achieved by providing a method to control a refrigerator, the method including reducing a temperature of a supercooling compartment in which food is placed below a freezing temperature; detecting electromagnetic radiation emitted when the food placed in the supercooling compartment begins to freeze; and applying energy to the food to prevent freezing of the food when the food emits electromagnetic radiation. 
     When a plurality of foods are placed in the supercooling compartment, electromagnetic radiation of each of the foods may be individually detected and energy may be individually applied to each of the foods. 
     The energy may be applied to the food upon detection of electromagnetic radiation emitted when an ice nucleus forms in the food. 
     The energy may be applied to the food upon detection of electromagnetic radiation emitted when an ice nucleus grows in the food. 
     The method may further include detecting a change in electromagnetic radiation when an ice nucleus is removed from the food while the energy is applied to the food and stopping the application of energy to the food. 
     Applying the energy to the food may include applying the energy to the food for a specific time. 
     The energy applied to the food may be thermal energy. 
     The method may further include storing information regarding electromagnetic radiation emitted when the food begins to freeze in a memory. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the present invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a front cross-sectional view schematically showing a refrigerator according to an embodiment of the present invention; 
         FIG. 2  is a side cross-sectional view schematically showing the refrigerator according to the embodiment of the present invention; 
         FIG. 3  is a block diagram showing main components of the refrigerator according to the embodiment of the present invention; 
         FIG. 4  is a front cross-sectional view showing a receptacle in the refrigerator according to the embodiment of the present invention; 
         FIG. 5  is a graph showing temperature change of water in a supercooling compartment; and 
         FIGS. 6 and 7  are a plan view and a front cross-sectional view showing another embodiment of the receptacle provided in the refrigerator according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the embodiments of a refrigerator and a method to control the same according to the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures. 
     As shown in  FIGS. 1 to 3 , a refrigerator according to an embodiment of the present invention includes a body  10  having freezing, cooling, and supercooling compartments  11 ,  12 , and  13 , a cooling unit  20  to provide cool air to the freezing, cooling and supercooling compartments  11 ,  12 , and  13 , a plurality of receptacles  42  provided in the supercooling compartment  13 , a plurality of electromagnetic radiation sensors  45  to detect electromagnetic radiation emitted from beverages contained in each of the receptacles  42 , a plurality of electric heaters  46  to provide thermal energy to beverages contained in each of the receptacles  42  to prevent freezing of the beverages, and a controller  51  to control the overall operation of the refrigerator. 
     The interior of the body  10  is divided into the freezing compartment  11  and the cooling compartment  12  by a central dividing wall  31 . A door  16  is mounted on the body  10  to open and close the freezing compartment  11  and the cooling compartment  12 . Cool air generated by the cooling unit  20  is provided to the freezing compartment  11  and the cooling compartment  12  through a plurality of cool air inlets  14  and  15  connected to the interior of the body  10 . This allows the freezing compartment  11  to be maintained at a freezing temperature (for example, in a range of −18° C. to −21° C.) which can sufficiently freeze food and allows the cooling compartment  12  to be maintained at a cooling temperature (for example, in a range of 3° C. to 5° C.) which can cool food. As with general cooling units, the cooling unit  20  includes a compressor  21  to compress refrigerant, a condenser (not shown) to condense refrigerant, a decompressor (not shown) to decompress refrigerant, an evaporator (not shown) to evaporate refrigerant, and a blower (not shown) to blow cool air generated by the evaporator into the cool air inlets  14  and  15 . 
     The supercooling compartment  13  is provided under the cooling compartment  12  and is separated from the cooling compartment  12  by a dividing wall  35 . A mixing compartment  17  in which cool air of the freezing compartment  11  and cool air of the cooling compartment  12  are mixed is provided above the supercooling compartment  13 . The mixing compartment  17  and the supercooling compartment  13  are separated from each other by a separation plate  18 . The central dividing wall  31  has an inlet  32  through which cool air of the freezing compartment  11  can be blown into the mixing compartment  17  and the dividing wall  35  above the mixing compartment  17  has an inlet  36  through which cool air of the cooling compartment  12  can be blown into the mixing compartment  17 . Blower fans  33  and  37  for smooth blowing of cool air and flaps  34  and  38 , which are opened or closed depending on activation of the blower fans  33  and  37 , are provided in the inlets  32  and  36 , respectively. When the blower fans  33  and  37  are activated, the flaps  34  and  38  are opened so that cool air of the freezing compartment  11  and cool air of the cooling compartment  12  are blown into the mixing compartment  17 . 
     In the mixing compartment  17 , cool air of the freezing compartment  11  and cool air of the cooling compartment  12  are mixed to generate cool air at a supercooling temperature (for example, in a range of −8° C. to −12° C.) which can supercool beverages. The cool air at the supercooling temperature is introduced into the supercooling compartment  13  through a cool air supply hole  19  formed in the separation plate  18 . The temperature of cool air generated in the mixing compartment  17  is controlled by the amounts of cool air blown therein by the blower fans  33  and  37 . The controller  51  controls the operations of the blower fans  33  and  37  based on a detection signal received from a temperature sensor  52  provided in the supercooling compartment  13 . The temperature of the supercooling compartment  13  is maintained to be equal to the temperature of the cool air generated in the mixing compartment  17 . 
     A tray  41  is slidably mounted in the supercooling compartment  13  and a plurality of receptacles  42  to contain beverages are provided in the tray  41 . Since each of the receptacles  42  must be electrically connected to the controller  51 , it is desirable that the tray  41  not be allowed to be completely separated from the body  10 , while still being movable, and each receptacle  42  can be fixed to the tray  41 . 
     As shown in  FIGS. 3 and 4 , each of the receptacles  42  has a plurality of receiving portions  43  and a plurality of receiving rooms  44  where beverages can be placed. Each of the receiving portions  43  and the receiving rooms  44  is designed to have a bottom area and a circumference appropriate to receive various sizes of commercial beverage containers. An electromagnetic radiation sensor  45  is provided under each receiving portion  43  and an electric heater  46  is provided around each receiving room  44  as an energy supply to apply energy to a beverage in the receiving room  44 . 
     Each electromagnetic radiation sensor  45  and each electric heater  46  are electrically connected to the controller  51 . The controller  51  receives a detection signal generated by each electromagnetic radiation sensor  45  and individually activates each electric heater  46  according to the detection signal. When the controller  51  activates the electric heater  46 , the electric heater  46  provides thermal energy to a beverage contained in the receiving room  44 . The electric heater  46  may be any type of heating element, which can generate heat through electrical control, such as a heating wire or a heat lamp. The electric heater  46  may be replaced with another energy supply which can apply a different type of energy than thermal energy to a beverage to prevent freezing of the beverage. 
     The electromagnetic radiation sensor  45  is a sensor that detects electromagnetic radiation emitted by a beverage and can be implemented in various forms using known electromagnetic radiation detection technologies. In particular, the electromagnetic radiation sensor  45  in the present invention detects electromagnetic radiation emitted when a beverage begins to freeze. Generally, beverages include mostly water and it is thus possible to determine the time when a beverage begins to freeze by detecting electromagnetic radiation emitted or a change in electromagnetic radiation emitted when water in the beverage begins to freeze through the electromagnetic radiation sensor  45 . 
     It is known that water emits electromagnetic radiation in a specific frequency band when the water begins to freeze to form an ice nucleus or when an ice nucleus grows. This fact is described in an article “PRORODA(NATURE), No. 9, 2000, Shibkov A. A., Zheltov M. A. and Korolev A. A. “Intrinsic Electromagnetic Radiation of Towering Ice”), Http://courier.com.ru/priroda/pr0900cont.htm” published in Russia. This article showed that water emits electromagnetic radiation in a band of 101-102 Hz when an ice nucleus begins to form in the water and electromagnetic radiation in a band of 103-106 Hz when an ice nucleus grows to begin to crystallize. 
     When a beverage emits electromagnetic radiation in a band of 101-102 Hz or electromagnetic radiation in a band of 103-106 Hz, the electromagnetic radiation sensor  45  detects the electromagnetic radiation and transmits the detection signal to the controller  51  and then the controller  51  immediately activates an electric heater  46  corresponding to the beverage to prevent freezing of the beverage. 
     According to the embodiment of the present invention, a database regarding specific frequencies of electromagnetic radiation emitted when ice nuclei form in various commercial beverages or specific frequencies of electromagnetic radiation emitted when ice nuclei grow in various commercial beverages may be produced and stored in a memory  54 . This makes it possible to determine a more accurate time when a given beverage begins to freeze. 
     The controller  51  controls the overall operation of the refrigerator and is connected to the cooling unit  20 , the blower fans  33  and  37 , the temperature sensor  52 , a plurality of signal amplifiers  47 , an input unit  53 , the memory  54 , and an RFID reader  55  as shown in  FIG. 3 . Here, the signal amplifiers  47  amplify detection signals that are transmitted from the electromagnetic radiation sensors  45  to the controller  51 . 
     The input unit  53  and the RFID reader  55  provide information regarding beverages contained in the supercooling compartment  13  to the controller  51  so that the temperature of the supercooling compartment  13  is adjusted to suit the characteristics of the beverages and that thermal energy is applied to the beverages at appropriate times. The information regarding the beverages (for example, a range of supercool temperatures, appropriate supercool temperatures, supercool temperature limits, a band of frequencies of electromagnetic radiation emitted when an ice nucleus forms, and a band of frequencies of electromagnetic radiation emitted when an ice nucleus grows) is stored in the memory  54 . The controller  51  controls the temperature of the supercooling compartment  13  based on the information stored in the memory  54  so that a selected beverage is maintained at an appropriate or maximum supercooled level and activates the electric heater  46  when the beverage begins to freeze. 
     The input unit  53  allows a user to input information required for control such as the types of beverages contained in the supercooling compartment  13 , reference supercool temperatures set according to beverages, and a band of frequencies of electromagnetic radiation in which the electric heater  46  is to be activated. The RFID reader  55  detects RFID tags (not shown) attached to containers of beverages contained in the supercooling compartment  13  and transmits the detection information of the beverages to the controller  51 . As known in the art, an RFID tag attached to a container of a beverage stores identification (ID) of the beverage. The controller  51  determines the type of a beverage to be stored through a signal received from the RFID reader  55  and controls the operation of the refrigerator based on the information regarding the beverage stored in the memory  54 . 
     In the refrigerator according to the embodiment of the present invention constructed as described above, when beverages are contained in the receptacles  42  of the supercooling compartment  13 , the controller  51  controls the temperature of the supercooling compartment  13  so that each beverage is maintained at an appropriate or maximum supercooled level to suit the characteristics of the beverage. The electromagnetic radiation sensor  45  detects electromagnetic radiation emitted from each beverage in the supercooling compartment  13  while the beverage is cooled at a temperature, less than or equal to a freezing temperature TF, along a temperature line ‘a’ as shown in  FIG. 5 . 
     The temperature of the supercooling compartment  13  may vary while the controller  51  maintains the temperature of the supercooling compartment  13  at a temperature less than or equal to the freezing temperature TF of each beverage. If the temperature of the supercooling compartment  13  varies to reach a supercool temperature limit TL of each beverage, an ice nucleus may form in the beverage while the temperature of the beverage rapidly changes along a temperature line ‘b’ so that the beverage freezes at the freezing temperature TF. When the temperature of the beverage reaches the supercool temperature limit TL so that the beverage begins to freeze, the beverage emits electromagnetic radiation in a specific frequency band (for example, a band of 101-102 Hz) as an ice nucleus begins to form in the beverage or electromagnetic radiation in a band of 103-106 Hz as an ice nucleus grows. The corresponding electromagnetic radiation sensor  45  detects electromagnetic radiation in the specific frequency band emitted from the beverage and generates a detection signal. The detection signal is transmitted to the controller  51  after being amplified by the signal amplifier  47 . The controller  51  then activates the electric heater  46  corresponding to the beverage to prevent freezing of the beverage. 
     While the electric heater  46  applies thermal energy to the beverage, the corresponding electromagnetic radiation sensor  45  constantly detects electromagnetic radiation emitted from the beverage. If the frequency of the emitted electromagnetic radiation is changed while ice nuclei in the beverage are removed, the electromagnetic radiation sensor  45  detects this change and transmits the detection signal to the controller  51  and the controller  51  then deactivates the electric heater  46  according to the detection signal. This operation of the electric heater  46  allows the temperature of the beverage to be maintained at an appropriate supercool temperature TO as shown by a temperature line C without being reduced to the supercool temperature limit TL. The activation of the electric heater  46  can be controlled based on time. In this case, after activating the electric heater  46  for a specific time, the controller  51  deactivates the electric heater  46  to prevent freezing of the beverage. 
     Even if no information regarding beverages contained in the supercooling compartment  13  is stored in the memory  54 , by detecting electromagnetic radiation emitted from each beverage through the electromagnetic radiation sensor  45 , the controller  51  can determine the time when the beverage begins to freeze and activate the electric heater  46  to prevent freezing of the beverage at the time. The controller  51  can update the beverage information in the memory  54  by storing new beverage information in the memory  54  using a detection signal received from the temperature sensor  52  or a detection signal received from the electromagnetic radiation sensor  45 . 
       FIGS. 6 and 7  show a different type of receptacle  61  that can be installed in the supercooling compartment  13  of the refrigerator according to the embodiment of the present invention. 
     The receptacle  61  shown in  FIGS. 6 and 7  has no individual receiving rooms to allow beverages to be smoothly received and removed and a plurality of receiving portions  62  where beverages can be placed are provided at one portion of the receptacle  61 . An electromagnetic radiation sensor  63  is provided in each receiving portion  62  to detect electromagnetic radiation emitted from a beverage placed on the receiving portion  62 . An electric heater  64  is also provided at one side of each receiving portion  62  to apply thermal energy to a beverage placed on the receiving portion  62  to prevent freezing of the beverage in a supercooled state. 
     Here, we omit a description of detailed operations of each electromagnetic radiation sensor  63  and each electric heater  64  since they are similar to those of the embodiment shown in  FIGS. 3 and 4 . 
     The refrigerator according to the embodiment of the present invention may also be provided with a dedicated non-metal container B to contain each beverage to form slush. In the case of beverages contained in metal containers among commercial beverages, electromagnetic radiation emitted from each beverage when it begins to freeze may be shielded by the metal containers. If the beverage is supercooled after being transferred into a dedicated non-metal container B, the electromagnetic radiation sensor  45  can effectively detect electromagnetic radiation emitted from the beverage. 
     The embodiment of the present invention can be applied not only to maintain a beverage in a supercooled state to form slush but also to maintain the freshness of food other than a beverage using an electromagnetic radiation sensor and an energy supply. For example, it is possible to keep food stored in a refrigerator fresh without freezing the food by producing and storing a database regarding electromagnetic radiation emitted when food stored in a refrigerator begins to freeze in the memory  54  and detecting electromagnetic radiation emitted from the stored food and then applying energy to the food according to the detection. 
     As is apparent from the above description, the embodiment of the present invention provides a refrigerator and a method to control the same with a variety of features and advantages. For example, electromagnetic radiation emitted from each beverage in a supercooled state when the beverage begins to freeze is detected and energy is applied to the beverage according to the detection, thereby stably keeping the beverage in a supercooled state. 
     In addition, a change in the state of each beverage stored in the supercooling compartment is individually detected to individually prevent freezing of each beverage. Thus, it is not necessary to accurately control the temperature of the supercooling compartment according to the characteristics of beverages stored in the supercooling compartment and therefore temperature control of the refrigerator is not complex. 
     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.