Abstract:
Disclosed is an icemaker for a refrigerator includes an ice mold for receiving water and freezing the water to ice, an ejector pivotally installed on the ice mold to eject the ice out of the ice mold, a motor for operating the ejector, a heater body disposed enclosing the ice mold to separate the ice from an inner surface of the ice mold by uniformly heating the ice mold, and a heating coil for applying induced electromotive power to the heater body, thereby allowing the heater body to generate heat.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an icemaker for a refrigerator, and more particularly, to an icemaker for a refrigerator, which can quickly separate pieces of ice therefrom by uniformly heating a surface where the pieces of ice contact an ice mold. 
   2. Description of the Related Art 
     FIG. 1  shows a refrigerator according to the related art. 
   Referring to  FIG. 1 , a refrigerator comprises a barrier  1  for dividing an inner space into a chilling compartment and a freezing compartment, a main body  2  in which a cooling cycle device for maintaining the chilling and freezing compartments at a low temperature is installed, a freezing door  4  pivotally mounted on the main body  2  to open and close the freezing compartment, and a chilling door  6  pivotally mounted on the main body  2  to open and close the chilling compartment. 
   The cooling cycle device applied to the refrigerator includes a compressor (not shown) for compressing low temperature/low pressure gas refrigerant, a condenser (not shown) for condensing the compressed refrigerant, an expanding device for reducing pressure of the condensed refrigerant, and a vaporizer for vaporizing the expanded refrigerant while absorbing heat of the chilling and freezing compartments. 
   In recent years, an automatic machine for making pieces of ice using cold air in the freezing compartment and dispensing the pieces of ice has been employed for user&#39;s convenience. 
   The automatic ice machine includes an icemaker  7  for freezing water fed thereto and an ice bank  20  for storing pieces of ice separated from the icemaker  7 , a dispenser  300  installed on the freezing door  4  to allow the pieces of ice to be dispensed even without opening the freezing door  4 , and an ice chute  40  for directing the pieces of ice from the ice bank  20  to the dispense  30 . 
   When the water is fed to the icemaker  7 , the water is frozen by the cool air in the freezing compartment. When the water is frozen, the pieces of ice are separated from the icemaker  7 . Therefore, there are a couple of technical requirements for (a) feeding a proper amount of water to the icemaker so as for the water not to overflow the icemaker, (b) feeding a proper cool air to quickly freeze the water, (c) easily separating the ice from the icemaker, and (d) easily directing the pieces of ice to the ice bank  20 . 
   Among the technical requirements, the separation of the ice from the icemaker by applying appropriate heat has been particularly developed. For example, a heating wire is arranged on an outer surface of the icemaker in a predetermined pattern where lines are spaced away from each other at a predetermined distance. When power is applied to the heating wire, the heating wire generates Joule heat to melt a portion of ice at a portion where the ice contacts the icemaker so that the ice can be effectively separated from the icemaker. U.S. Pat. No. 6,705,091 assigned to the applicant of this invention discloses such an icemaker with the heating wire. 
   However, the method for separating the ice from the icemaker by using the joule heat generated by the heating wire has a couple of drawbacks as follows: 
   1. Since the lines of the wire are spaced away from each other, the heat is not uniformly applied to an entire surface where the icemaker contacts the ice. Therefore, a large amount of heat must be applied to separate the ice from the icemaker, increasing the power consumption as well as the ice making time. 
   2. Since the heat is locally applied, the shape of the pieces of ice is not identical. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention is directed to an icemaker for a refrigerator that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
   An object of the present invention is to provide an icemaker that can quickly separate pieces of heating a surface of an ice mold, thereby making pieces of ice that are formed in an identical shape and saving the time for making the ice. 
   Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
   To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, an icemaker for a refrigerator comprises an ice mold for receiving water and freezing the water to ice; an ejector pivotally installed on the ice mold to eject the ice out of the ice mold; a motor for operating the ejector; a heater body disposed enclosing the ice mold to separate the ice from an inner surface of the ice mold by uniformly heating the ice mold; and a heating coil for applying induced electromotive power to the heater body, thereby allowing the heater body to generate heat. 
   In another aspect of the present invention, there is provided an icemaker for a refrigerator, comprising an ice mold for receiving water and freezing the water to ice; and a heater for separating the ice from an inner surface of the ice mold by uniformly heating a surface where the ice contacts the inner surface of the ice mold using an induction heating manner by an induced electromotive power applied form an external side. 
   In still another aspect of the present invention, there is provided an icemaker for a refrigerator, comprising an ice mold for receiving water and freezing the water to ice; and a heater for separating the ice from an inner surface of the ice mold by uniformly heating an entire surface of the ice mold. 
   It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
       FIG. 1  is a refrigerator according to the related art; 
       FIG. 2  is a perspective view of an icemaker according to an embodiment of the present invention; 
       FIG. 3  is a partially broken perspective view of an icemaker according to an embodiment of the present invention; 
       FIG. 4  is a sectional view taken along line A-A′ of  FIG. 2 ; 
       FIG. 5  is a view illustrating an induction heating principle; 
       FIG. 6  is a hysteresis loop according to an induction heating; and 
       FIGS. 7 and 8  are views illustrating a process for separating ice from an icemaker using a heater. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     FIGS. 2 and 3  show an icemaker according to an embodiment of the present invention. 
   Referring to  FIGS. 2 and 3 , an icemaker  10  comprises a cup  11  for storing water fed from a water supply hose (not shown), an ice mold  12  for receiving the water from the cup  11  and freezing the water using cool air in a freezing compartment, a heater  130  for heating the ice mold  12  to separate pieces of the ice, the heater  130  being mounted on the ice mold  12 , an ejector  14  for ejecting the pieces of the ice out of the ice mold  12 , the ejector  14  being pivotally mounted on the ice mold  14 , a motor (not shown) for generating torque for driving the ejector  14 , a slider  16  for directing the pieces of the ice ejected by the ejector  14  to the ice bank  20 , a detecting lever  17  for detecting the ice bank  20  fully filled with the pieces of the ice, a controller  18  for, in accordance with whether the ice bank  20  is fully filled with the pieces of the ice, controlling a temperature of the ice mold  12 , the operations of the heater  130 , the motor, and a water supply valve controlling the water supply to the cup  11 . 
   The ice mold  12  is provided with a space in which the water is frozen and a plurality of partition  121  for dividing the space into a plurality of freezing sections to make the pieces of the ice. The ice mold  12  is further provided at a rear end with connection parts  122  for fixing the icemaker  10  on a rear wall of the freezing compartment. 
   The ejector  14  comprises a pivoting shaft  141  installed on the ice mold  12  and pivoted by the torque of the motor and a plurality of scoops  142  extending from the pivoting shaft  141 . The number of the scoops  142  is identical to that of the freezing sections divided by the partitions  121 . The scoops  142  are located in the respective freezing sections to scoop the corresponding pieces of the ice out of the freezing sections. The motor is installed in the controller  18  disposed on a side of the ice mold  12  and is connected to the pivoting shaft  141 . 
   The controller  18  may be provided with a temperature sensor for detecting a temperature of the ice mold  12  and an ice detecting sensor for detecting a rotating position of the detecting lever  17  to determine if the ice bank is fully filled with the pieces of the ice. 
   The heater  130  may be formed of an induction heater that can uniformly heat the ice mold  12 . 
   The operation of the icemaker will be briefly described hereinafter. 
   The water is first fed to the ice mold  12  via the cup  11  and is then frozen, after which a surface of the frozen water is uniformly heated by the heater  130  such that the pieces of the ice can be separated at a surface where they contact the ice mold  12 . Then, the pieces of the ice are ejected out of the ice mold. That is, as the pivoting shaft  141  pivots, the pieces of the ice are scooped by the scoops  142 . The scooped pieces of the ice are stacked in the ice bank  20  along the slider  16 . 
     FIG. 4  is a sectional view taken along line A-A′ of  FIG. 2 . 
   As shown in the drawing, there are shown the ice mold  12 , the ejector  14  and the slider  16 . The heater  130  is disposed on a circumferential outer bottom of the ice mold  12 . The heater  130  is designed to be heated by an induction heating manner. 
   That is, the heater  130  comprises a heating coil generating eddy current by high frequency current applied from an external side to convert the electric energy into the thermal and a heater body  134  in which the heating coil is buried, the heater body  134  being formed in a circular arc shape to enclose the circumferential outer bottom of the ice mold  12 . The heater body  134  separates the pieces of the ice  21  from the inner surface of the ice mold  12  using induction energy inducted from the heating coil  132 . 
   An induction heating principle will be described hereinafter with reference to the accompanying drawings. 
     FIG. 5  is a view illustrating an induction heating principle, and  FIG. 6  is a hysteresis loop according to an induction heating. 
   Referring first to  FIG. 5 , an electric conductor in a coil along which alternating current (high frequency current) flows generates heat by an eddy current loss and a hysteresis loss (in case of a magnetic body). That is, the induction heating is realized by such heat generated by the eddy current loss and the hysteresis loss. Particularly, a high frequency induction heating uses high frequency current. 
   At this point, as shown in  FIG. 5 , alternating magnetic flux (high frequency magnetic flux) is generated in a coil along which alternating current (high frequency current) i 1  and induced current (induced electromotive force) is generated in the electric conductor in a magnetic field. Particularly, the current generated by the electromotive force is called eddy current. When the eddy current flows along the electric conductor (to-be-heated-object) having a predetermined amount of resistance, the electric conductor generates the Joule heat. This is called the eddy current loss that will be a primary heat source in the induction heating. The eddy current loss can be illustrated as the following formula according to Joule&#39;s law.
 
We=ne f 2  Bm 2  (ne: a constant, f: frequency, Bm: a magnetic flux density)
 
   As illustrated by the formula, the eddy current loss is proportional to the square of the frequency. Therefore, when the frequency is higher than 100 kHz, the heating is realized by the eddy current loss. When the frequency is less than 100 kHz, the heating is realized by the hysteresis loss. 
   When the to-be-heated-object is formed of magnetic material and alternating current is applied to a heating coil wound around the to-be-heated object, the to-be-heated-object is magnetized. At this point, when intensity of the magnetic field is gradually increased, a curve representing the variation of the magnetic flux density B is not identical to that representing the magnetic field intensity H. That is, as shown in  FIG. 6 , a loop shape is defined by the curves, providing a hysteresis phenomenon. This loop shape is called a hysteresis loop. 
   Particularly, the larger the area defined by the hysteresis loop, the higher the hysteresis loss. That is, as the area defined by the hysteresis loop is increased, the high frequency induction heating efficiency is increased in the induction heating. This can be illustrated as the following formula.
 
 Wh=nh f Bm 1.6 ( wb/m   2 ) (nh: a constant of applied metal core, f: frequency, and Bm: magnetic flux density)
 
   When the frequency is increased above 50 kHz, since the eddy current loss proportional to the square of the frequency becomes greater than the hysteresis loss. In addition, when the frequency is further increased, the hysteresis loss may be almost ignored. When magnetic or nonmagnetic material such as Cu or Al is heated above a transformation point, the hysteresis loss does occur. That is, the heating is realized only by the eddy current loss. 
   In the present invention, the heating body  134  functions as the electric conductor along which induced current flows when alternating current is applied to the heating coil  132 . 
   The separation process of the ice from the ice mold  12  will be described hereinafter with reference to the accompanying drawings. 
     FIG. 7  shows a heating process by the heater  130  before the ejector  14  is operated, and  FIG. 8  shows an ejecting process by the ejector  14  after the ice is separated from the inner surface of the ice mold  12 . 
   Referring first to  FIG. 7 , when the water is completely frozen in the ice mold  12  to form the ice  21 , the ice  21  is closely adhered to the inner surface of the ice mold  12 . In order to separate the ice  21  from the inner surface of the ice mold  12 , electric power is applied to the heater  130  disposed on the circumferential outer bottom of the ice mold  12 . 
   That is, when the electric power is applied to the heater  130 , eddy current is generated by the heating coil of the heater  130 . The eddy current flows along the heater body  134  to covert the electric energy into the thermal energy, thereby generating the Joule heat in the heater body  134 . At this point, since the eddy current flows through the entire area of the heater body  134 , the heater body  134  uniformly generates the heat through its entire area. 
   When the ice mold  12  is uniformly heated by the heat uniformly generated through the entire area of the heater body  134 , as shown in  FIG. 7 , the adhering portion of the ice to the inner surface of the ice mold  12  uniformly melts, making it easy to quickly separate the ice from the ice mold  12 . As described above, since the ice mold  12  is uniformly heated by the induction heating manner, the ice  21  can be more quickly separated from the ice mold  12 . 
   When the adhering portion of the ice to the inner surface of the ice mold  12  melts, as shown in  FIG. 8 , the shaft  141  of the ejector  14  is rotated by the motor such that the scoop  142  can scoop the ice  21  out of the ice mold  12 , thereby directing the ice  21  to the ice bank  20 . 
   Meanwhile, the heating coil  132  is buried in the heater body  134 . However, the present invention is not limited to this case. That is, the heating coil  132  may be formed on a surface of the heater body  134  in a predetermined pattern. Preferably, the heater body  134  is formed of metal having a predetermined amount of resistance, and the heating coil  132  is formed in a predetermined pattern having a uniformly spaced line through the entire area of the heater body  134 . In addition, the heater body  134  is designed corresponding to the circumferential outer bottom of the ice mold  12  so that the heat conduction can be quickly realized. 
   When the ice mold  12  is formed of conductive material such as metal, the heat generated by induction heating can be directly transmitted to the ice, making it possible to more quickly make the ice. In this case, the induced heating coil may be directly formed on an outer surface of the ice mold  12 . 
   The above-described icemaker can be applied to a side-by-side type refrigerator as well as freeze-top-type refrigerator. 
   In the icemaker of the present invention, since the ice mold  12  is uniformly heated by the induction heating manner, the pieces of the ice  21  can be more quickly separated from the ice mold  12 , being formed in an identical shape. 
   Furthermore, the electric power used for the ice separation as well as the ice making time can be saved. 
   It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.