Patent Publication Number: US-2020300527-A1

Title: Ice maker and refrigerator

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority to Korean Patent Application No. 10-2019-0033167, filed in the Korean Intellectual Property Office on Mar. 22, 2019, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to an ice maker and a refrigerator. 
     In general, refrigerators are home appliances for storing foods at a low temperature in a storage space that is covered by a door. 
     The refrigerator may cool the inside of the storage space by using cold air to store the stored food in a refrigerated or frozen state. 
     Generally, an ice maker for making ice is provided in the refrigerator. 
     The ice maker is constructed so that water supplied from a water supply source or a water tank is accommodated in a tray to make ice. 
     Also, the ice maker is constructed to transfer the made ice from the ice tray in a heating manner or twisting manner. 
     As described above, the ice maker through which water is automatically supplied, and the ice automatically transferred may be opened upward so that the mode ice is pumped up. 
     As described above, the ice made in the ice maker may have at least one flat surface such as crescent or cubic shape. 
     When the ice has a spherical shape, it is more convenient to ice the ice, and also, it is possible to provide different feeling of use to a user. Also, even when the made ice is stored, a contact area between the ice cubes may be minimized to minimize a mat of the ice cubes. 
     The cited reference, Korean Patent No. 10-1850918 discloses an ice maker. 
     The ice maker of the cited reference includes an upper tray on which a plurality of hemispherical upper cells are arranged and which includes a pair of link guides extending upward from opposite lateral ends, a lower tray on which a plurality of hemispherical lower cells are arranged and which is rotatably connected to the upper tray, a rotation axis connected to rear ends of the lower tray and the upper tray and configured to rotate the lower tray with respect to the upper tray, a pair of links having one end connected to the lower tray and the other end connected to the link guide, and an upper ejecting pin assembly which has opposite ends respectively connected to the pair of links while being inserted into the link guide and ascends and descends along with the link. 
     In the cited reference, although spherical ice is generated by the hemispherical upper cell and the hemispherical lower cell, the ice is simultaneously generated by the upper cell and the lower cell, and thus bubbles included in water are dispersed in water rather than being completely discharged, and accordingly, generated ice is disadvantageously opaque. 
     In addition, a plurality of cells are arranged in a line, and thus heat transfer between cool air and cells positioned at opposite ends of the plurality of cells is maximized. In this case, ice is rapidly generated in cells positioned at the opposite ends of the plurality of cells, and thus water is moved to cells positioned between the opposite ends by expansive force when water at the opposite ends of the cells is phase-changed to ice and there is a problem a spherical shape of ice is deformed. 
     SUMMARY 
     The present embodiment provides an ice maker and a refrigerator in which cool air is concentrated into an upper side of an ice chamber to equalize speeds at which ices are generated in a plurality of ice chambers. 
     The present embodiment provides an ice maker and a refrigerator for making transparent ice. 
     The present embodiment provides an ice maker and a refrigerator for equalizing the transparency of ice irrespective of a type of a refrigerator with an ice maker installed therein. 
     The present embodiment provides an ice maker and a refrigerator for preventing a portion at which a driver for rotating a lower tray is installed from being deformed during a rotation procedure in which the lower tray repeatedly reciprocates. 
     The present embodiment provides an ice maker and a refrigerator for preventing a lower tray from interfering with an upper tray during a rotation procedure of the lower tray. 
     The present embodiment provides a refrigerator including the aforementioned ice maker. 
     According to an embodiment, an ice maker includes first and second trays configured to form a plurality of ice chambers configured to make ice, and an upper case including a cool air hole through which cool air passes, and a tray opening configured to allow the first tray to contact the cool air passing through the cool air hole. 
     The upper case may further include the cool air guide configured to guide the cool air passing through the cool air hole toward the tray opening. 
     The second tray may be disposed below the first tray, and a portion of the first tray may penetrate the tray opening. 
     The first tray may include a plurality of upper openings configured to guide the cool air to the plurality of ice chambers. 
     The plurality of ice chambers may be arranged in a line in a direction to be away from the cool air hole. 
     The cool air guide may include a first vertical guide and a second vertical guide spaced apart from the first vertical guide. 
     The first vertical guide and the second vertical guide may form a guidance path configured to guide the cool air passing through the cool air hole toward the tray opening. 
     An upper end of the first and second vertical guides may be positioned higher than the tray opening. 
     The upper end of each of the first and second vertical guides may be positioned at the same height or positioned higher than an upper opening of the first tray. 
     A cross-sectional area of at least a portion of the guidance path may be reduced in a direction away from the cool air hole. 
     A first imaginary line that bisects a horizontal length of the cool air hole and extends in a horizontal direction, and a second imaginary line that connects centers of the plurality of ice chambers and extends in a horizontal direction may be spaced apart from each other. 
     The second imaginary line may penetrate the first vertical guide after passing along the guidance path. 
     One end of the first vertical guide may be positioned at an opposite side to the second imaginary line based on the first imaginary line, and the plurality of ice chambers may include a first ice chamber closest to the cool air hole, and a second ice chamber adjacent to the first ice chamber. 
     Other end of the first vertical guide may be positioned closer to an upper opening of the second ice chamber than an upper opening of the first ice chamber. 
     The first vertical guide may extend to be rounded in a horizontal direction from the one end toward the other end. 
     One end of the second vertical guide may be positioned at an opposite side to the one end of the first vertical guide in the cool air hole, and at least a portion of the first ice chamber may be positioned between other end of the second vertical guide and the other end of the first vertical guide. 
     The ice maker may further include a driver configured to move the second tray, and a connector configured to transfer power of the driver to the second tray. 
     The upper case may further include an through-opening that the connector penetrates. 
     The cool air guide may guide a flow of cool air to allow the cool air passing through the cool air hole to flow toward the plurality of ice chambers before flowing toward the through-opening. 
     The through-opening may include a first through-opening positioned adjacent to the cool air hole, and a second through-opening spaced apart from the first through-opening. At least a portion of the tray opening may be positioned between the first through-opening and the second through-opening. 
     The second vertical guide may be positioned closer to the first through-opening than the first vertical guide. 
     The cool air guide may further include a horizontal guide configured to guide the cool air passing through the cool air hole. The horizontal guide may extend from a position that is the same or is lower than a lowermost point of the cool air hole. 
     According to another embodiment, a refrigerator includes a storage compartment configured to store a food material, and an ice maker configured to phase-change water of an ice chamber to ice by cool air supplied to the storage compartment. 
     The ice maker may include first and second trays configured to form a plurality of ice chambers, and an upper case configured to support the first tray. 
     The plurality of ice chambers may be arranged in a line in a direction to be away from a cool air hole. The upper case may include the cool air hole through which cool air passes, and a cool air guide configured to guide the cool air passing through the cool air hole toward the plurality of ice chambers. 
     The second tray may be disposed below the first tray, and the upper case may include a tray opening that the first tray penetrates. The cool air guide may guide the cool air toward the tray opening. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a refrigerator according to an embodiment. 
         FIG. 2  is a view illustrating a state in which a door of the refrigerator of FIG.  1  is opened. 
         FIG. 3  is a perspective view of an ice maker viewed from above according to an embodiment. 
         FIG. 4  is a perspective view of an ice maker viewed from below according to an embodiment. 
         FIG. 5  is an exploded perspective view of an ice maker according to an embodiment. 
         FIGS. 6A and 6B  are perspective views of an upper case according to an embodiment. 
         FIG. 7  is a view showing an upper case viewed from a side of a cool air hole. 
         FIG. 8  is a view showing the case in which cool air passing through a cool air hole flows in an ice maker. 
         FIG. 9  is an upper perspective view of an upper tray according to an embodiment. 
         FIG. 10  is a lower perspective view of an upper tray according to an embodiment. 
         FIG. 11  is a side view of an upper tray according to an embodiment. 
         FIG. 12  is an upper perspective view of an upper support according to an embodiment. 
         FIG. 13  is a lower perspective view of an upper support according to an embodiment. 
         FIG. 14  is an enlarged view of a heater coupling part in the upper case of  FIG. 6B . 
         FIG. 15  is a cross-sectional view illustrating a state in which an upper assembly is assembled. 
         FIG. 16  is a perspective view of a lower assembly according to an embodiment. 
         FIG. 17  is an upper perspective view of a lower case according to an embodiment. 
         FIG. 18  is a lower perspective view of a lower case according to an embodiment. 
         FIGS. 19 and 20  are perspective views of a lower tray viewed from above according to an embodiment. 
         FIG. 21  is a perspective view of a lower tray viewed from below according to an embodiment. 
         FIG. 22  is a plan view of a lower tray according to an embodiment. 
         FIG. 23  is a side view of a lower tray according to an embodiment. 
         FIG. 24  is a top perspective view of the lower support according to an embodiment. 
         FIG. 25  is a bottom perspective view of the lower support according to an embodiment. 
         FIG. 26  is a cross-sectional view taken along  26 - 26  of  FIG. 16  for showing the state in which the lower assembly is assembled. 
         FIG. 27  is a cross-sectional view taken along  27 - 27  of  FIG. 3 . 
         FIG. 28  is a view illustrating the state in which ice is completely made in  FIG. 27 . 
         FIG. 29  is a cross-sectional view taken along  29 - 29  of  FIG. 3  in the state in which water is supplied. 
         FIG. 30  is a cross-sectional view taken along  29 - 29  of  FIG. 3  in the state in which ice is made. 
         FIG. 31  is a cross-sectional view taken along  29 - 29  of  FIG. 2  in the state in which ice is completely made. 
         FIG. 32  is a cross-sectional view taken along  29 - 29  of  FIG. 3  in an early stage in which ice is transferred. 
         FIG. 33  is a cross-sectional view taken along  29 - 29  of  FIG. 3  at a position at which full ice is detected. 
         FIG. 34  is a cross-sectional view taken along  29 - 29  of  FIG. 3  at a position at which ice is completely transferred. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  is a perspective view of a refrigerator according to an embodiment, and  FIG. 2  is a view illustrating a state in which a door of the refrigerator of  FIG. 1  is opened. 
     Referring to  FIGS. 1 and 2 , a refrigerator  1  according to an embodiment may include a cabinet  2  defining a storage space and a door that opens and closes the storage space. 
     In detail, the cabinet  2  may define the storage space that is vertically divided by a barrier. Here, a refrigerating compartment  3  may be defined at an upper side, and a freezing compartment  4  may be defined at a lower side. 
     Accommodation members such as a drawer, a shelf, a basket, and the like may be provided in the refrigerating compartment  3  and the freezing compartment  4 . 
     The door may include a refrigerating compartment door  5  opening/closing the refrigerating compartment  3  and a freezing compartment door  6  opening/closing the freezing compartment  4 . 
     The refrigerating compartment door  5  may be constituted by a pair of left and right doors and be opened and closed through rotation thereof. Also, the freezing compartment door  6  may be inserted and withdrawn in a drawer manner. 
     Alternatively, the arrangement of the refrigerating compartment  3  and the freezing compartment  4  and the shape of the door may be changed according to kinds of refrigerators, but are not limited thereto. For example, the embodiments may be applied to various kinds of refrigerators. For example, the freezing compartment  4  and the refrigerating compartment  3  may be disposed at left and right sides, or the freezing compartment  4  may be disposed above the refrigerating compartment  3 . 
     An ice maker  100  may be provided in the freezing compartment  4 . The ice maker  100  is constructed to make ice by using supplied water. Here, the ice may have a spherical shape. 
     Also, an ice bin  102  in which the ice is stored after being transferred from the ice maker  100  may be further provided below the ice maker  100 . 
     The ice maker  100  and the ice bin  102  may be mounted in the freezing compartment  4  in a state of being respectively mounted in separate housings  101 . 
     The freezing compartment  4  may include a duct (not shown) for supplying cool air to the ice maker  100 . Air discharged from the duct may flow in the ice maker  100  and may then flow in the freezing compartment  4 . 
     A user may open the refrigerating compartment door  6  to approach the ice bin  102 , thereby obtaining the ice. 
     In another example, a dispenser for dispensing purified water or the made ice to the outside may be provided in the refrigerating compartment door  5 . 
     Also, the ice made in the ice maker  100  or the ice stored in the ice bin  102  after being made in the ice maker  100  may be transferred to the dispenser by a transfer unit. Thus, the user may obtain the ice from the dispenser. 
     Hereinafter, the ice maker will be described in detail with reference to the accompanying drawings. 
       FIG. 3  is a perspective view of an ice maker viewed from above according to an embodiment.  FIG. 4  is a perspective view of an ice maker viewed from below according to an embodiment.  FIG. 5  is an exploded perspective view of an ice maker according to an embodiment. 
     Referring to  FIGS. 3 to 5 , the ice maker  100  may include an upper assembly  110  and a lower assembly  200 . 
     The lower assembly  200  may movable with respect to the upper assembly  110 . For example, the lower assembly  200  may be connected to be rotatable with respect to the upper assembly  110 . 
     In a state in which the lower assembly  200  contacts the upper assembly  110 , the lower assembly  200  together with the upper assembly  110  may make spherical ice. 
     That is, the upper assembly  110  and the lower assembly  200  may define an ice chamber  111  for making the spherical ice. The ice chamber  111  may have a chamber having a substantially spherical shape. 
     The upper assembly  110  and the lower assembly  200  may define a plurality of ice chambers  111 . 
     Hereinafter, a structure in which three ice chambers are defined by the upper assembly  110  and the lower assembly  200  will be described as an example, and also, the embodiments are not limited to the number of ice chambers  111 . 
     In the state in which the ice chamber  111  is defined by the upper assembly  110  and the lower assembly  200 , water is supplied to the ice chamber  111  through a water supply part  190 . 
     The water supply part  190  is coupled to the upper assembly  110  to guide water supplied from the outside to the ice chamber  111 . 
     After the ice is made, the lower assembly  200  may rotate in a forward direction. Thus, the spherical ice made between the upper assembly  110  and the lower assembly  200  may be separated from the upper assembly  110  and the lower assembly  200 . 
     The ice maker  100  may further include a driver  180  so that the lower assembly  200  is rotatable with respect to the upper assembly  110 . 
     The driver  180  may include a driving motor and a power transmission part for transmitting power of the driving motor to the lower assembly  200 . The power transmission part may include one or more gears. 
     The driving motor may be a bi-directional rotatable motor. Thus, the lower assembly  200  may rotate in both directions. 
     The ice maker  100  may further include an upper ejector  300  so that the ice is capable of being separated from the upper assembly  110 . 
     The upper ejector  300  may be constructed so that the ice closely attached to the upper assembly  110  is separated from the upper assembly  110 . 
     The upper ejector  300  may include an ejector body  310  and one or more upper ejecting pins  320  extending in a direction crossing the ejector body  310 . 
     The upper ejecting pins  320  may be provided in the same number of ice chambers  111 . 
     A separation prevention protrusion  312  for preventing a connector  350  from being separated in the state of being coupled to the connector  350  that will be described later may be provided on each of both ends of the ejector body  310 . 
     For example, the pair of separation prevention protrusions  312  may protrude in opposite directions from the ejector body  310 . 
     While the upper ejecting pin  320  passing through the upper assembly  110  and inserted into the ice chamber  111 , the ice within the ice chamber  111  may be pressed. 
     The ice pressed by the upper ejecting pin  320  may be separated from the upper assembly  110 . 
     Also, the ice maker  100  may further include a lower ejector  400  so that the ice closely attached to the lower assembly  200  is capable of being separated. 
     The lower ejector  400  may press the lower assembly  200  to separate the ice closely attached to the lower assembly  200  from the lower assembly  200 . For example, the lower ejector  400  may be fixed to the upper assembly  110 . 
     The lower ejector  400  may include an ejector body  410  and one or more lower ejecting pins  420  protruding from the ejector body  410 . The lower ejecting pins  420  may be provided in the same number of ice chambers  111 . 
     While the lower assembly  200  rotates to transfer the ice, rotation force of the lower assembly  200  may be transmitted to the upper ejector  300 . 
     For this, the ice maker  100  may further include a connector  350  connecting the lower assembly  200  to the upper ejector  300 . The connector  350  may include one or more links. 
     For example, the connector  350  may include a first link  352  for rotating the lower support  270 , and a second link  356  connected to the lower support  270  and configured to transfer rotational force of the lower support  270  to the upper ejector  300  when the lower support  270  rotates. 
     For example, when the lower assembly  200  rotates in one direction, the upper ejector  300  may descend by the connector  350  to allow the upper ejector pin  320  to press the ice of the ice chamber  111 . 
     On the other hand, when the lower assembly  200  rotates in the other direction, the upper ejector  300  may ascend by the connector  350  to return to its original position. 
     Hereinafter, the upper assembly  110  and the lower assembly  200  will be described in more detail. 
     The upper assembly  110  may include an upper tray  150  defining a portion of the ice chamber  111  making the ice. For example, the upper tray  150  may define an upper portion of the ice chamber  111 . 
     The upper assembly  110  may further include an upper support  170  fixing a position of the upper tray  150 . 
     The upper support  170  may restrict downward movement of the upper tray  150 . 
     The upper assembly  110  may further include an upper case  120  fixing a position of the upper tray  150 . 
     The upper tray  150  may be disposed below the upper case  120 . 
     As described above, the upper case  120 , the upper tray  150 , and the upper support  170 , which are vertically aligned, may be coupled to each other through a coupling member. 
     That is, the upper tray  150  may be fixed to the upper case  120  through coupling of the coupling member. 
     For example, the water supply part  190  may be fixed to the upper case  120 . 
     The ice maker  100  may further include a temperature sensor  500  detecting a temperature of the ice chamber  111 . 
     In one example, the temperature sensor  500  detects the temperature of the upper tray  150  thus to indirectly detect the temperature of the water or the temperature of the ice in the ice chamber  111 . 
     For example, the temperature sensor  500  may be mounted on the upper case  120 . Also, when the upper tray  150  is fixed to the upper case  120 , the temperature sensor  500  may contact the upper tray  150 . 
     The lower assembly  200  may include a lower tray  250  defining the other portion of the ice chamber  111  making the ice. For example, the lower tray  250  may define a lower portion of the ice chamber  111 . 
     The lower assembly  200  may further include a lower support  270  supporting a lower portion of the lower tray  250 . 
     The lower assembly  200  may further include a lower case  210  of which at least a portion covers an upper side of the lower tray  250 . 
     The lower case  210 , the lower tray  250 , and the lower support  270  may be coupled to each other through a coupling member. 
     The ice maker  100  may further include a switch for turning on/off the ice maker  100 . When the user turns on the switch  600 , the ice maker  100  may make ice. 
     That is, when the switch  600  is turned on, water may be supplied to the ice maker  100 . Then, an ice making process of making ice by using cold air and an ice separating process of transferring the ice through the rotation of the lower assembly  200 . 
     On the other hand, when the switch  600  is manipulated to be turned off, the making of the ice through the ice maker  100  may be impossible. For example, the switch  600  may be provided in the upper case  120 . 
     The ice maker  100  may further include a full ice detection lever  700 . 
     For example, the full ice detection lever  700  may detect whether the ice bin  102  is filled with ice while receiving power of the driver  180  and rotating. 
     One side of the full ice detection lever  700  may be connected to the driver  180  and the other side of the full ice detection lever  700  may be connected to the upper case  120 . 
     For example, the other side of the full ice detection lever  700  may be rotatably connected to the upper case  120  below a connection shaft  370  of the connector  350 . 
     Thus, the rotational center of the full ice detection lever  700  may be positioned below the connection shaft  370 . 
     The driver  180  may include a motor and a plurality of gears for transferring power of the motor to the lower assembly. 
     The driver  180  may further include a cam that rotates by receiving rotation power of the motor, and a moving lever that moves along a surface of the cam. The moving lever may include the magnet. The driver  180  may further include a hall sensor for detecting the magnet during a procedure in which the moving lever moves. 
     A first gear coupled to the full ice detection lever  700  among a plurality of gears of the driver  180  may be selectively coupled or decoupled to and from a second gear engaged with the first gear. For example, the first gear may be elastically supported by an elastic member and may be engaged with the second gear in a state in which external force is not applied. 
     In contrast, when higher resistance than elastic force of the elastic member is applied to the first gear, the first gear may be spaced apart from the second gear. 
     An example of the case in which higher resistance than elastic force of the elastic member is applied to the first gear may include the case in which the full ice detection lever  700  is restrained by ice during a produce of transferring ice (when the ice bin  102  is filled with ice). In this case, the first gear may be spaced apart from the second gear, and thus gears may be prevented from being damaged. 
     The full ice detection lever  700  may be operatively associated with the lower assembly  200  and may be rotated while the lower assembly  200  is rotated, by the plurality of gears and the cam. In this case, the cam may be connected to the second gear or may be operatively associated with the second gear. 
     According to whether the hall sensor detects a magnet, the hall sensor may output a first signal and a second signal that are different. Any one of the first signal may be a high signal and the other one may be a low signal. 
     The full ice detection lever  700  may be rotated to a position at which whether the ice bin  102  is filled with ice from a standby position (a position of the lower assembly, at which ice is made) in order to detect whether the ice bin  102  is filled with ice. 
     In the state in which the full ice detection lever  700  is positioned at the standby position, at least a portion of the full ice detection lever  700  may be positioned below the lower assembly  200 . 
     The full ice detection lever  700  may include a detection body  710 . The detection body  710  may be positioned at the lowermost side during a rotation procedure of the full ice detection lever  700 . 
     An entire portion of the detection body  710  may be positioned below the lower assembly  200  in order to prevent the lower assembly  200  and the detection body  710  from interfering with each other during a rotation procedure of the lower assembly  200 . 
     The detection body  710  may contact ice in the ice bin  102  in the state in which ice is filled with the ice bin  102 . 
     The full ice detection lever  700  may be a wire type lever. That is, the full ice detection lever  700  may be formed by bending a wire with a predetermined diameter a plurality of number of times. 
     The full ice detection lever  700  may include the detection body  710 . The detection body  710  may extend in a parallel direction to a direction in which the connection shaft  370  extends. 
     The detection body  710  may be positioned lower than a lowermost point of the lower assembly  200  irrespective of a position. 
     The full ice detection lever  700  may further include a pair of extension parts  720  and  730  that extend upward at opposite ends of the detection body  710 . 
     The pair of extension parts  720  and  730  may extend substantially parallel to each other. 
     The pair of extension parts  720  and  730  may include a first extension part  720  and a second extension part  730 . 
     A horizontal length of the detection body  710  may be larger than a vertical length of each of the pair of extension parts  720  and  730 . 
     An interval between the pair of extension parts  720  and  730  may be larger than a horizontal length of the lower assembly  200 . 
     Thus, during a rotation procedure of the full ice detection lever  700  and a rotation procedure of the lower assembly  200 , the pair of extension parts  720  and  730  and the lower assembly  200  may be prevented from interfering with each other. 
     Each of the pair of extension parts  720  and  730  may include first extension bars  722  and  732  that extend from the detection body  710 , and second extension bars  721  and  731  that extend from the first extension bars  722  and  732  to be inclined at a predetermined angle. 
     The full ice detection lever  700  may further include a pair of couplers  740  and  750  that are bent at ends of the pair of extension parts  720  and  730  and extend. 
     The pair of couplers  740  and  750  may include a first coupler  740  that extends from the first extension part  720  and a second coupler  750  that extends from the second extension part  730 . 
     For example, the pair of couplers  740  and  750  may extend from the second extension bars  721  and  731 . 
     The first coupler  740  and the second coupler  750  may extend in a direction to be spaced apart from the extension parts  720  and  730 , respectively. 
     The first coupler  740  may be connected to the driver  180 , and the second coupler  750  may be connected to the upper case  120 . 
     At least a portion of the first coupler  740  may extend in a horizontal direction. That is, at least a portion of the first coupler  740  may be positioned in parallel to the detection body  710 . 
     The first coupler  740  and the second coupler  750  may provide the rotational center of the full ice detection lever  700 . 
     According to the present embodiment, the second coupler  750  may be coupled to the upper case  120  in an idle state. Thus, the first coupler  740  may substantially provide the rotational center of the full ice detection lever  700 . 
     The first coupler  740  may include a first horizontal extension part  741  that extends in a horizontal direction from the first extension part  720 . 
     The first coupler  740  may further include a bent portion  742  bent from the first horizontal extension part  741 . 
     Without being limited to, the bent portion  742  may be inclined downward in a direction to be spaced apart from the first horizontal extension part  741  and may then be inclined upward. 
     For example, the bent portion  742  may include a first inclination portion  742   a  that is inclined downward from the first horizontal extension part  741 , and a second inclination portion  742   b  that is inclined upward from the first inclination portion  742   a.    
     A boundary portion between the first inclination portion  742   a  and the second inclination portion  742   b  may be positioned at the lowermost side of the first coupler  740 . 
     The first coupler  740  includes the bent portion  742  in order to increase coupling force with the driver  180 . 
     The first coupler  740  may further include a second horizontal extension part  743  that extends in a horizontal direction from an end of the bent portion  742 . 
     For example, the second horizontal extension part  743  may extend in a horizontal direction from the second inclination portion  742   b.    
     The second horizontal extension part  743  and the first horizontal extension part  741  may be positioned at the same height based on the detection body  710 . That is, the first horizontal extension part  741  and the second horizontal extension part  743  may be positioned at the same extension line. 
     In another example, according to the present embodiment, the first coupler  740  may include only the first horizontal extension part  741  or may also include only the first horizontal extension part  741  and the bent portion  742 . 
     Alternatively, the first coupler  740  may include only the bent portion  742  and the second horizontal extension part  743 . 
     The second coupler  750  may include a coupling body  751  that extends in a horizontal direction from the second extension part  730 , and a flange body  752  bent from the coupling body  751 . 
     For example, the coupling body  751  may extend in parallel to the flange body  752 . 
     For example, the flange body  752  may extend in upward and downward directions. The flange body  752  may extend downward from the coupling body  751 . 
     The flange body  752  may extend in parallel to the second extension part  730 . 
     The second coupler  750  may penetrate the upper case  120 . The upper case  120  may include a hole  120   a  that the second coupler  750  penetrates. 
     &lt;Upper Case&gt; 
       FIGS. 6A and 6B  are perspective views of an upper case according to an embodiment.  FIG. 7  is a view showing an upper case viewed from a side of a cool air hole.  FIG. 8  is a view showing the case in which cool air passing through a cool air hole flows in an ice maker. 
     Referring to  FIGS. 6 to 8 , the upper case  120  may be fixed to a housing  101  within the freezing compartment  4  in a state in which the upper tray  150  is fixed. 
     The upper case  120  may include an upper plate for fixing the upper tray  150 . 
     The upper tray  150  may be fixed to the upper plate  121  in a state in which a portion of the upper tray  150  contacts a bottom surface of the upper plate  121 . 
     A tray opening  123  through which a portion of the upper tray  150  passes may be defined in the upper plate  121 . 
     For example, when the upper tray  150  is fixed to the upper plate  121  in a state in which the upper tray  150  is disposed below the upper plate  121 , a portion of the upper tray  150  may protrude upward from the upper plate  121  through the tray opening  123 . 
     Alternatively, the upper tray  150  may not protrude upward from the upper plate  121  through tray opening  123  but protrude downward from the upper plate  121  through the tray opening  123 . 
     The upper plate  121  may include a recess  122  that is recessed downward. The tray opening  123  may be defined in a bottom surface  122   a  of the recess  122 . 
     Thus, the upper tray  150  passing through the tray opening  123  may be disposed in a space defined by the recess  122 . 
     A heater coupling part  124  for coupling an upper heater (see reference numeral  148  of  FIG. 14 ) that heats the upper tray  150  so as to transfer the ice may be provided in the upper case  120 . 
     For example, the heater coupling part  124  may be provided on the upper plate  121 . The heater coupling part  124  may be disposed below the recess  122 . 
     The upper case  120  may further include a plurality of installation ribs  128  and  129  for installing the temperature sensor  500 . 
     The pair of installation ribs  128  and  129  may be disposed to be spaced apart from each other in a direction of an arrow B of  FIG. 6B . The pair of installation ribs  128  and  129  may be disposed to face each other, and the temperature sensor  500  may be disposed between the pair of installation ribs  128  and  129 . 
     The pair of installation ribs  128  and  129  may be provided on the upper plate  121 . 
     A plurality of slots  131  and  132  coupled to the upper tray  150  may be provided in the upper plate  121 . 
     A portion of the upper tray  150  may be inserted into the plurality of slots  131  and  132 . 
     The plurality of slots  131  and  132  may include a first upper slot  131  and a second upper slot  132  disposed at an opposite side of the first upper slot  131  with respect to the tray opening  123 . 
     The tray opening  123  may be defined between the first upper slot  131  and the second upper slot  132 . 
     The first upper slot  131  and the second upper slot  132  may be spaced apart from each other in a direction of an arrow B of  FIG. 6B . 
     Although not limited, the plurality of first upper slots  131  may be arranged to be spaced apart from each other in a direction of an arrow A (hereinafter, referred to as a first direction) that a direction crossing a direction of an arrow B (hereinafter, referred to as a second direction). 
     Also, the plurality of second upper slots  132  may be arranged to be spaced apart from each other in the direction of the arrow A. 
     In this specification, the direction of the arrow A may be the same direction as the arranged direction of the plurality of ice chambers  111 . 
     For example, the first upper slot  131  may be defined in a curved shape. Thus, the first upper slot  131  may increase in length. 
     For example, the second upper slot  132  may be defined in a curved shape. Thus, the second upper slot  132  may increase in length. 
     When each of the upper slots  131  and  132  increases in length, a protrusion (that is disposed on the upper tray) inserted into each of the upper slots  131  and  132  may increase in length to improve coupling force between the upper tray  150  and the upper case  120 . 
     A distance between the first upper slot  131  and the tray opening  123  may be different from that between the second upper slot  132  and the tray opening  123 . For example, the distance between the first upper slot  131  and the tray opening  123  may be greater than that between the second upper slot  132  and the tray opening  123 . 
     Also, when viewed from the tray opening  123  toward each of the upper slots  131 , a shape that is convexly rounded from each of the slots  131  toward the outside of the tray opening  123  may be provided. 
     The upper plate  121  may further include a sleeve  133  into which a coupling boss of the upper support, which will be described later, is inserted. 
     The sleeve  133  may have a cylindrical shape and extend upward from the upper plate  121 . 
     For example, a plurality of sleeves  133  may be provided on the upper plate  121 . The plurality of sleeves  133  may be arranged to be spaced apart from each other in the direction of the arrow A. Also, the plurality of sleeves  133  may be arranged in a plurality of rows in the direction of the arrow B. 
     A portion of the plurality of sleeves may be disposed between the two first upper slots  131  adjacent to each other. 
     The other portion of the plurality of sleeves may be disposed between the two second upper slots  132  adjacent to each other or be disposed to face a region between the two second upper slots  132 . 
     The upper case  120  may further include a plurality of hinge supports  135  and  136  allowing the lower assembly  200  to rotate. 
     The plurality of hinge supports  135  and  136  may be disposed to be spaced apart from each other in the direction of the arrow A with respect to  FIG. 6B . Also, a first hinge hole  137  may be defined in each of the hinge supports  135  and  136 . 
     For example, the plurality of hinge supports  135  and  136  may extend downward from the upper plate  121 . 
     The plurality of hinge supports  135  and  136  and the tray opening  123  may be spaced apart from each other in a direction indicated by arrow B. 
     The upper case  120  may include may include through-opening  139   b  and  139  that a portion of the connector  350  penetrates. For example, the second link  356  positioned at each of opposite sides of the lower assembly  200  may penetrate through-openings  139   b  and  139   c.    
     The through-openings  139   b  and  139   c  may be spaced apart from each other in a direction indicated by arrow A. For example, the through-openings  139   b  and  139   c  may be formed in the upper plate  121 . 
     The upper case  120  may further include a vertical extension part  140  vertically extending along a circumference of the upper plate  121 . The vertical extension part  140  may extend upward from the upper plate  121 . 
     The vertical extension part  140  may include one or more coupling hooks  140   a . The upper case  120  may be hook-coupled to the housing  101  by the coupling hooks  140   a.    
     The water supply part  190  may be coupled to the vertical extension part  140 . 
     The upper case  120  may further include a horizontal extension part  142  horizontally extending to the outside of the vertical extension part  140 . 
     A screw coupling part  142   a  protruding outward to screw-couple the upper case  120  to the housing  101  may be provided on the horizontal extension part  142 . 
     The upper case  120  may further include a side circumferential part  143 . The side circumferential part  143  may extend downward from the horizontal extension part  142 . 
     The side circumferential part  143  may be disposed to surround a circumference of the lower assembly  200 . That is, the side circumferential part  143  may prevent the lower assembly  200  from being exposed to the outside. 
     Although the upper case is coupled to the separate housing  101  within the freezing compartment  4  as described above, the embodiment is not limited thereto. For example, the upper case  120  may be directly coupled to a wall defining the freezing compartment  4 . 
     The side circumferential part  143  may include a first side wall  143   a  in which a cool air hole  134  is formed, and a second side wall  143   b  disposed to face the first side wall  143   a.    
     The first side wall  143   a  and the second side wall  143   b  may be spaced apart from each other in a direction indicated by arrow A. 
     When the ice maker  100  is installed in the freezing compartment  4 , the first side wall  143   a  may face a rear wall of the freezing compartment  4  or one wall of opposite walls of the freezing compartment  4 . 
     The lower assembly  200  may be positioned between the first side wall  143   a  and the second side wall  143   b.    
     The full ice detection lever  700  rotates, and thus the side circumferential part  143  may include an anti-interference groove  148  formed therein in order to prevent interference during a rotation procedure of the full ice detection lever  700 . 
     The through-openings  139   b  and  139   c  may include a first through-opening  139   b  positioned adjacent to the first side wall  143   a , and a second through-opening  139  positioned adjacent to the second side wall  143   b . The first through-opening  139   b  may be positioned more adjacent to the cool air hole  134  than the second through-opening  139   c.    
     At least a portion of the tray opening  123  may be positioned between the through-opening  139   b  and  139   c.    
     The cool air hole  134  may be formed to be long in right and left directions from the first side wall  143   a.    
     The lowermost point of the cool air hole  134  may be positioned lower than the lowermost point of the upper plate  121  or at the same height as the lowermost point of the upper plate  121 . 
     At least a portion of the upper tray  150  may be positioned higher than the tray opening  123  of the upper plate  121  based on the upper plate  121 . In contrast, the lower tray  250  may be positioned lower than the tray opening  123  of the upper plate  121 . 
     Thus, heat of a portion of cool air may be directly or indirectly transferred to the upper tray  150  from an upper side of the upper plate  121 , and heat of another portion of the cool air may be directly or indirectly transferred to the lower tray  250  from a lower side of the upper plate  121 . 
       FIG. 8  shows a first imaginary line L 1  that bisects the horizontal length of the cool air hole  134  and extends in a horizontal direction, and a second imaginary line L 2  that connects the centers of the plurality of ice chambers  111  and extends in a horizontal direction. 
     The first imaginary line L 1  may be positioned in parallel to the second imaginary line L 2  rather than being matched with each other. Thus, the first imaginary line L 1  and the second imaginary line L 2  may be spaced apart from each other in a direction indicated by arrow B. 
     According to an embodiment, the upper case  120  may include a cool air guide  145  in order to guide cool air passing through the cool air hole  134  toward the upper tray  150 . The cool air guide  145  may guide the cool air passing through the cool air hole  134  toward the tray opening  123 . 
     A flow of cool air according to whether the cool air guide  145  is present will be described. 
     When a cool air guide is not present in the upper case  120 , the first imaginary line L 1  is arranged in parallel to the second imaginary line L 2  as described above, and thus, from cool air passing through the cool air hole  134 , cool air at an opposite side to the second imaginary line L 2  based on the first imaginary line L 1  may flow straightly and may then may flow downward through the second through-opening  139   c.    
     In contrast, based on from cool air passing through the cool air hole  134 , a portion of cool air at the second imaginary line L 2  based on the first imaginary line L 1  may flow toward the upper tray, and another portion of the cool air at the second imaginary line L 2  may flow downward through the first through-opening  139   b.    
     As a result, when the cool air guide  145  is not present, based on cool air passing through the cool air hole  134 , the amount of cool air flowing in a downward direction of the upper plate  121  through the through-opening  139   b  and  139   c  may be larger than the amount of cool air flowing in a perpendicular direction of the upper tray  150 . 
     According to the present embodiment, the plurality of ice chambers  111  may be arranged in a line. When the amount of cool air below the upper plate  121  is equal to or larger than the amount of cool air above the upper plate  121 , a heat transfer of cool air between cool air and the ice chambers  111  at opposite ends among the plurality of ice chambers  111  may be larger than a heat transfer between cool air and the ice chamber  111  at the central part. This is because the cool air first transfers heat to the ice chambers  111  at the opposite ends and then flows toward the central part. 
     In this case, ice may be more rapidly generated at the ice chambers  111  at the opposite ends among the plurality of ice chambers  111 . 
     Water expands while being changed in phase, and in this regard, when ice is rapidly generated at opposite ends of the plurality of ice chambers  111 , expansive force of the water may be applied to the ice chamber  111  at the central part. Then, water in the ice chambers at the opposite ends between the upper tray  150  and the lower tray  250  may move toward the central part, and thus the shape of ice generated in the ice chamber  111  is not uniform, and manufactured ices may be disadvantageously connected. 
     Thus, according to the present embodiment, the upper case  120  may include the cool air guide  145  in such a way that cool air is concentrated into an upper side of the upper plate  121  and ices are manufactured at the same or similar speed in the plurality of ice chambers  111 . 
     The cool air guide  145  may include a horizontal guide  145   a  for guiding cool air passing through the cool air hole  134 , and a plurality of vertical guides  145   b  and  145   c.    
     The horizontal guide  145   a  may guide cool air in an upward direction of the upper plate  121  from a position that is the same position or a lower position than the lowermost point of the cool air hole  134 . 
     The horizontal guide  145   a  may connect the first side wall  143   a  and the upper plate  121 . 
     When a lowermost point  134   a  of the cool air hole  134  is positioned lower than a lowermost point of the upper plate  121 , the horizontal guide  145   a  may be inclined in an upward direction toward the upper plate  121  from the cool air hole  134 . 
     The plurality of vertical guides  145   b  and  145   c  may be arranged to cross the horizontal guide  145   a  or may be arranged perpendicular thereto. 
     The plurality of vertical guides  145   b  and  145   c  may include a first vertical guide  145   b  and a second vertical guide  145   c  spaced apart from the first vertical guide  145   b.    
     One end  145   ba  of the first vertical guide  145   b  may be positioned adjacent to the cool air guide  145 , and the other end  145   bb  may be positioned adjacent to the tray opening  123 . 
     For example, the plurality of ice chambers  111  may include a first ice chamber  111   a , a second ice chamber  111   b , and a third ice chamber  111   c  that are sequentially arranged in a direction to be spaced apart from the cool air hole  134 . 
     That is, the first ice chamber  111   a  may be positioned closest to the cool air hole  134 , and the third ice chamber  111   c  may be positioned farthest from the cool air hole  134 . 
     According to the present embodiment, the first ice chamber  111   a  and the third ice chamber  111   c  may be referred to as an opposite-end ice chamber. 
     Then, the other end  145   bb  of the first vertical guide  145   b  may be positioned in a region corresponding to a region between the first ice chamber  111   a  and the third ice chamber  111   c .  FIG. 8  shows an example in which the other end  145   bb  of the first vertical guide  145   b  is positioned adjacent to the second ice chamber  111   b.    
     The other end  145   bb  of the first vertical guide  145   b  may be positioned closer to an upper opening  154  of the second ice chamber  111   b  than the upper opening  154  of the first ice chamber  111   a.    
     The end  145   ba  of the first vertical guide  145   b  may be positioned at an opposite side to the second imaginary line L 2  based on the first imaginary line L 1 . 
     The first vertical guide  145   b  may extend to be round in a horizontal direction toward the other end  145   bb  from the end  145   ba  in such a way that the other end  145   bb  of the first vertical guide  145   b  is positioned adjacent to the second ice chamber  111   b.    
     For example, the first vertical guide  145   b  may include a first guide part  146   a , a second guide part  146   b  that extends with a different curvature from the first guide part  146   a , and a third guide part  146   c  that extends toward the second through-opening  139   c  from the second guide part  146   b.    
     In another example, each of the first guide part  146   a  and the second guide part  146   b  may extend in a straight line, and in this case, the second guide part  146   b  may extend to be inclined at a predetermined angle with respect to the first guide part  146   a.    
     The third guide part  146   c  may guide air flowing in the second guide part  146   b  to the second through-opening  139   c . Needless to say, the third guide part  146   c  may be omitted. Alternatively, the first vertical guide  145   b  may extend in a straight line and may be positioned adjacent to the second ice chamber  111   b.    
     The other end  145   bb  of the first vertical guide  145   b  may be positioned closer to the first ice chamber  111   a  than the third ice chamber  111   c  in such a way that cool air flow in the plurality of ice chambers sequentially or entirely. 
     When the other end  145   bb  of the first vertical guide  145   b  is positioned close to the third ice chamber  111   c , the air guided by the first vertical guide  145   b  may flow toward the third ice chamber  111   c  in the state in which the air does not flow in the first ice chamber  111   a  and the second ice chamber  111   b.    
     Thus, cool air does not flow in the plurality of ice chambers  111  sequentially or entirely, and thus ice may be made at different speeds in the plurality of ice chambers  111 . However, as seen from the upper perspective view of the upper tray, the other end  145   bb  of the first vertical guide  145   b  may be positioned closer to the first ice chamber  111   a  than the third ice chamber  111   c , and thus ice may be made at the same or similar speed in the plurality of ice chambers  111 . 
     The second vertical guide  145   c  may be spaced apart from the first vertical guide  145   b  in a direction indicated by arrow B. The second vertical guide  145   c  may form a guidance path  1467  with the first vertical guide  145   b . Upper ends of the first and second vertical guides  145   b  and  145   c  may be positioned higher than the tray opening  123 . The upper ends of the first and second vertical guides  145   b  and  145   c  may be positioned at the same height or higher than the upper opening  154  of t the upper tray  150 . 
     A horizontal length of the second vertical guide  145   c  may be shorter than a horizontal length of the first vertical guide  145   b.    
     One end  145   ca  of the second vertical guide  145   c  may be positioned adjacent to the cool air hole  134 . 
     In this case, the first imaginary line L 1  may be positioned between the end  145   ba  of the first vertical guide  145   b  and the end  145   ca  of the second vertical guide  145   c.    
     At least a portion of the second vertical guide  145   c  may extend toward the first vertical guide  145   b  from the end  145   ca . Thus, a cross-sectional area of at least a portion of the guidance path  1467  may be reduced in a direction away from the cool air hole  134 . 
     For example, a width of at least a portion of the guidance path  1467  in a horizontal direction may be reduced in a direction away from the cool air hole  134 . 
     A partial or entire portion of the second vertical guide  145   c  may be formed to be rounded. 
     The other end  145   cb  of the second vertical guide  145   c  may be positioned closer to the cool air hole  134  than the other end  145   bb  of the second vertical guide  145   c.    
     The other end  145   cb  of the second vertical guide  145   c  may be positioned in a region between the first imaginary line L 1  and the second imaginary line L 2 . 
     Viewed from the above, the upper case  120  may be configured in such a way that the second imaginary line L 2  penetrates the second vertical guide  145   c.    
     The second vertical guide  145   c  may substantially separate the cool air hole  134  and the first through-opening  139   b.    
     A horizontal distance to the other end  145   cb  of the second vertical guide  145   c  from the first side wall  143   a  may be formed to be longer than a maximum horizontal distance of the first through-opening  139   b  from the first side wall  143   a.    
     Thus, as shown in  FIG. 8 , a portion of cool air passing through the cool air hole  134  may flow along the second vertical guide  145   c , may be changed in direction after flowing toward at least the first ice chamber  111   a , and may then pass through the first through-opening  139   b.    
     One end of the second vertical guide  145   c  may be positioned in the cool air hole  134  at an opposite side to the end  145   ba  of the first vertical guide  145   b . At least a portion of the first ice chamber  111   a  may be positioned between the other end  145   cb  of the second vertical guide  145   c  and the other end  145   ba  of the first vertical guide  145   b.    
     Referring to  FIG. 8 , according to the present embodiment, cool air passing through the cool air hole  134  may be concentrated on into an upper side of the upper plate  121  by the cool air guide  145 , and cool air flowing in the upper plate  121  may pass through the first and second through-openings  139   b  and  139   c.    
     Thus, ice may be made at uniform speed in the plurality of ice chambers  111 , and thus spherical ice may be made, thereby preventing the ice from being connected with each other. 
     In the full ice detection lever  700 , the first coupler  740  may be connected to the driver  180 , and the second coupler  750  may be connected to the first side wall  143   a.    
     The driver  180  may be coupled to the second side wall  143   b . The lower assembly  200  may be rotated by the driver  180  during a procedure of transferring ice, and the lower tray  250  may be pressurized by the lower ejector  400 . 
     In this case, during a procedure in which the lower tray  250  is pressurized by the lower ejector  400 , relative movement between the driver  180  and the lower assembly  200  may be performed. 
     Pressurizing force for pressurizing the lower tray  250  by the lower ejector  400  may be transferred to an entire portion of the lower assembly  200 , and may also be transferred to the driver  180 . For example, torsion force may be applied to the driver  180 . 
     Then, force applied to the driver  180  may also be applied to the second side wall  143   b . When the second side wall  143   b  is deformed by force applied to the second side wall  143   b , relative movement between the connector  350  and the driver  180  installed on the second side wall  143   b  may be changed. In this case, there is a probability that an axis of the driver  180  and the connector  350  are decoupled from each other. 
     Thus, a structure for minimizing deformation of the second side wall  143   b  may be additionally included in the upper case  120 . 
     For example, the upper case  120  may further include one or more first ribs  148   a  for connection of the upper plate  121  and the vertical extension part  140 .  FIG. 6A  shows the case in which a plurality of first ribs  148   a  and  148   b  are arranged to be spaced apart from each other in a horizontal direction. 
     A wire guide part  148   c  for guiding a wire connected to the upper heater (see reference numeral  148  of  FIG. 14 ) or the lower heater (see reference numeral  296  of  FIG. 27 ) may be disposed between two adjacent first ribs  148   a  and  148   b  among the plurality of first ribs  148   a  and  148   b.    
     The upper plate  121  may include at least two steeped plates  121 . For example, the upper plate  121  may include a first plate  121   a , and a second plate  121   b  positioned higher than the first plate  121   a.    
     In this case, the tray opening  123  may be formed in the first plate  121   a.    
     The first plate  121   a  and the second plate  121   b  may be connected to each other by a connection wall  121   c . The upper plate  121  may further include one or more second ribs  148   d  for connecting the first plate  121   a  and the second plate  121   b , to the connection wall  121   c.    
     The upper plate  121  may further include a wire guide hook  147  for guiding a wire for connected to the upper heater (see reference numeral  148  of  FIG. 14 ) or the lower heater (see reference numeral  296  of  FIG. 27 ). For example, the wire guide hook  147  may be provided to be elastically modified with respect to the first plate  121   a.    
     &lt;Upper Tray&gt; 
       FIG. 9  is an upper perspective view of an upper tray according to an embodiment.  FIG. 10  is a lower perspective view of an upper tray according to an embodiment.  FIG. 11  is a side view of an upper tray according to an embodiment. 
     Referring to  FIGS. 9 to 11 , the upper tray  150  may be made of a non-metal material and a flexible material that is capable of being restored to its original shape after being deformed by an external force. 
     For example, the upper tray  150  may be made of a silicon material. Like this embodiment, when the upper tray  150  is made of the silicon material, even though external force is applied to deform the upper tray  150  during the ice separating process, the upper tray  150  may be restored to its original shape. Thus, in spite of repetitive ice making, spherical ice may be made. 
     If the upper tray  150  is made of a metal material, when the external force is applied to the upper tray  150  to deform the upper tray  150  itself, the upper tray  150  may not be restored to its original shape any more. 
     In this case, after the upper tray  150  is deformed in shape, the spherical ice may not be made. That is, it is impossible to repeatedly make the spherical ice. 
     On the other hand, like this embodiment, when the upper tray  150  is made of the flexible material that is capable of being restored to its original shape, this limitation may be solved. 
     Also, when the upper tray  150  is made of the silicon material, the upper tray  150  may be prevented from being melted or thermally deformed by heat provided from an upper heater that will be described later. 
     The upper tray  150  may include an upper tray body  151  defining an upper chamber  152  that is a portion of the ice chamber  111 . 
     The upper tray body  151  may be define a plurality of upper chambers  152 . 
     For example, the plurality of upper chambers  152  may define a first upper chamber  152   a , a second upper chamber  152   b , and a third upper chamber  152   c.    
     The upper tray body  151  may include three chamber walls  153  defining three independent upper chambers  152   a ,  152   b , and  152   c . The three chamber walls  153  may be connected to each other to form one body. 
     The first upper chamber  152   a , the second upper chamber  152   b , and the third upper chamber  152   c  may be arranged in a line. For example, the first upper chamber  152   a , the second upper chamber  152   b , and the third upper chamber  152   c  may be arranged in a direction of an arrow A with respect to  FIG. 10 . The direction of the arrow A of  FIG. 10  may be the same direction as the direction of the arrow A of  FIG. 7 . 
     The upper chamber  152  may have a hemispherical shape. That is, an upper portion of the spherical ice may be made by the upper chamber  152 . 
     An upper opening  154  may be defined in an upper side of the upper tray body  151 . The upper opening  154  may be communicated with the upper chamber  152 . 
     For example, three upper openings  154  may be defined in the upper tray body  151 . 
     Cold air may be guided into the ice chamber  111  through the upper opening  154 . Further, water may be supplied into the ice chamber  111  through the upper opening  154 . 
     In the ice separating process, the upper ejector  300  may be inserted into the upper chamber  152  through the upper opening  154 . 
     While the upper ejector  300  is inserted through the upper opening  154 , an inlet wall  155  may be provided on the upper tray  150  to minimize deformation of the upper opening  154  in the upper tray  150 . 
     The inlet wall  155  may be disposed along a circumference of the upper opening  154  and extend upward from the upper tray body  151 . 
     The inlet wall  155  may have a cylindrical shape. Thus, the upper ejector  30  may pass through the upper opening  154  via an inner space of the inlet wall  155 . 
     One or more first connection ribs  155   a  may be provided along a circumference of the inlet wall  155  to prevent the inlet wall  155  from being deformed while the upper ejector  300  is inserted into the upper opening  154 . 
     The first connection rib  155   a  may connect the inlet wall  155  to the upper tray body  151 . For example, the first connection rib  155   a  may be integrated with the circumference of the inlet wall  155  and an outer face of the upper tray body  151 . 
     Although not limited, the plurality of connection ribs  155   a  may be disposed along the circumference of the inlet wall  155 . 
     The two inlet walls  155  corresponding to the second upper chamber  152   b  and the third upper chamber  152   c  may be connected to each other through the second connection rib  162 . The second connection rib  162  may also prevent the inlet wall  155  from being deformed. 
     A water supply guide  156  may be provided in the inlet wall  155  corresponding to one of the three upper chambers  152   a ,  152   b , and  152   c.    
     Although not limited, the water supply guide  156  may be provided in the inlet wall corresponding to the second upper chamber  152   b.    
     The water supply guide  156  may be inclined upward from the inlet wall  155  in a direction which is away from the second upper chamber  152   b.    
     The upper tray  150  may further include a first accommodation part  160 . The heater coupling part  124  of the upper case  120  may be accommodated in the first accommodation part  160 . 
     An upper heater (see reference numeral  148  of  FIG. 14 ) may be provided in the heater coupling part  124 . Thus, it may be understood that the upper heater (see reference numeral  148  of  FIG. 14 ) is accommodated in the first accommodation part  160 . 
     The first accommodation part  160  may be disposed in a shape that surrounds the upper chambers  152   a ,  152   b , and  152   c . The first accommodation part  160  may be provided by recessing a top surface of the upper tray body  151  downward. 
     The first accommodation part  160  may be positioned lower than the upper opening  154 . 
     The upper tray  150  may further include a second accommodation part  161  (or referred to as a sensor accommodation part) in which the temperature sensor  500  is accommodated. 
     For example, the second accommodation part  161  may be provided in the upper tray body  151 . Although not limited, the second accommodation part  161  may be provided by recessing a bottom surface of the first accommodation part  160  downward. 
     Also, the second accommodation part  161  may be disposed between the two upper chambers adjacent to each other. For example, the second accommodation part  161  may be disposed between the first upper chamber  152   a  and the second upper chamber  152   b.    
     Thus, an interference between the upper heater (see reference numeral  148  of  FIG. 14 ) accommodated in the first accommodation part  160  and the temperature sensor  500  may be prevented. 
     In the state in which the temperature sensor  500  is accommodated in the second accommodation part  161 , the temperature sensor  500  may contact an outer face of the upper tray body  151 . 
     The chamber wall  153  of the upper tray body  151  may include a vertical wall  153   a  and a curved wall  153   b.    
     The curved wall  153   b  may be rounded upward in a direction that is away from the upper chamber  152 . 
     The upper tray  150  may further include a horizontal extension part  164  horizontally extending from the circumference of the upper tray body  151 . For example, the horizontal extension part  164  may extend along a circumference of an upper edge of the upper tray body  151 . 
     The horizontal extension part  164  may contact the upper case  120  and the upper support  170 . 
     For example, a bottom surface  164   b  (or referred to as a “first surface”) of the horizontal extension part  164  may contact the upper support  170 , and a top surface  164   a  (or referred to as a “second surface”) of the horizontal extension part  164  may contact the upper case  120 . 
     At least a portion of the horizontal extension part  164  may be disposed between the upper case  120  and the upper support  170 . 
     The horizontal extension part  164  may include a plurality of upper protrusions  165  and  166  respectively inserted into the plurality of upper slots  131  and  132 . 
     The plurality of upper protrusions  165  and  166  may include a first upper protrusion  165  and a second upper protrusion  166  disposed at an opposite side of the first upper protrusion  165  with respect to the upper opening  154 . 
     The first upper protrusion  165  may be inserted into the first upper slot  131 , and the second upper protrusion  166  may be inserted into the second upper slot  132 . 
     The first upper protrusion  165  and the second upper protrusion  166  may protrude upward from the top surface  164   a  of the horizontal extension part  164 . 
     The first upper protrusion  165  and the second upper protrusion  166  may be spaced apart from each other in the direction of the arrow B of  FIG. 10 . The direction of the arrow B of  FIG. 10  may be the same direction as the direction of the arrow B of  FIG. 7 . 
     Although not limited, the plurality of first upper protrusions  165  may be arranged to be spaced apart from each other in the direction of the arrow A. 
     The plurality of second upper protrusions  166  may be arranged to be spaced apart from each other in the direction of the arrow A. 
     For example, the first upper protrusion  165  may be provided in a curved shape. Also, for example, the second upper protrusion  166  may be provided in a curved shape. 
     In this embodiment, each of the upper protrusions  165  and  166  may be constructed so that the upper tray  150  and the upper case  120  are coupled to each other, and also, the horizontal extension part is prevented from being deformed during the ice making process or the ice separating process. 
     Here, when each of the upper protrusions  165  and  166  is provided in the curved shape, distances between the upper protrusions  165  and  166  and the upper chamber  152  in a longitudinal direction of the upper protrusions  165  and  166  may be equal or similar to each other to effectively prevent the horizontal extension parts  264  from being deformed. 
     For example, the deformation in the horizontal direction of the horizontal extension part  264  may be minimized to prevent the horizontal extension part  264  from being plastic-deformed. If when the horizontal extension part  264  is plastic-deformed, since the upper tray body is not positioned at the correct position during the ice making, the shape of the ice may not close to the spherical shape. 
     The horizontal extension part  164  may further include a plurality of lower protrusions  167  and  168 . The plurality of lower protrusions  167  and  168  may be inserted into a lower slot of the upper support  170 , which will be described below. 
     The plurality of lower protrusions  167  and  168  may include a first lower protrusion  167  and a second lower protrusion  168  disposed at an opposite side of the first lower protrusion  167  with respect to the upper chamber  152 . 
     The first lower protrusion  167  and the second lower protrusion  168  may protrude downward from the bottom surface  164   b  of the horizontal extension part  164 . 
     The first lower protrusion  167  may be disposed at an opposite to the first upper protrusion  165  with respect to the horizontal extension part  164 . The second lower protrusion  168  may be disposed at an opposite side of the second upper protrusion  166  with respect to the horizontal extension part  164 . 
     The first lower protrusion  167  may be spaced apart from the vertical wall  153   a  of the upper tray body  151 . The second lower protrusion  168  may be spaced apart from the curved wall  153   b  of the upper tray body  151 . 
     Each of the plurality of lower protrusions  167  and  168  may also be provided in a curved shape. Since the protrusions  165 ,  166 ,  167 , and  168  are disposed on each of the top and bottom surfaces  164   a  and  164   b  of the horizontal extension part  164 , the deformation in the horizontal direction of the horizontal extension part  164  may be effectively prevented. 
     A through-hole  169  through which the coupling boss of the upper support  170 , which will be described later, may be provided in the horizontal extension part  164 . 
     For example, a plurality of through-holes  169  may be provided in the horizontal extension part  164 . 
     A portion of the plurality of through-holes  169  may be disposed between the two first upper protrusions  165  adjacent to each other or the two first lower protrusions  167  adjacent to each other. 
     The other portion of the plurality of through-holes  169  may be disposed between the two second lower protrusions  168  adjacent to each other or be disposed to face a region between the two second lower protrusions  168 . 
     &lt;Upper Support&gt; 
       FIG. 12  is an upper perspective view of an upper support according to an embodiment.  FIG. 13  is a lower perspective view of an upper support according to an embodiment. 
     Referring to  FIGS. 12 and 13 , the upper support  170  may include a support plate  171  contacting the upper tray  150 . 
     For example, a top surface of the support plate  171  may contact the bottom surface  164   b  of the horizontal extension part  164  of the upper tray  150 . 
     A plate opening  172  through which the upper tray body  151  passes may be defined in the support plate  171 . 
     A circumferential wall  174  that is bent upward may be provided on an edge of the support plate  171 . For example, the circumferential wall  174  may contact at least a portion of a circumference of a side surface of the horizontal extension part  164 . 
     Also, a top surface of the circumferential wall  174  may contact a bottom surface of the upper plate  121 . 
     The support plate  171  may include a plurality of lower slots  176  and  177 . 
     The plurality of lower slots  176  and  177  may include a first lower slot  176  into which the first lower protrusion  167  is inserted and a second lower slot  177  into which the second lower protrusion  168  is inserted. 
     The plurality of first lower slots  176  may be disposed to be spaced apart from each other in the direction of the arrow A on the support plate  171 . Also, the plurality of second lower slots  177  may be disposed to be spaced apart from each other in the direction of the arrow A on the support plate  171 . 
     The support plate  171  may further include a plurality of coupling bosses  175 . The plurality of coupling bosses  175  may protrude upward from the top surface of the support plate  171 . 
     Each of the coupling bosses  175  may pass through the through-hole  169  of the horizontal extension part  164  and be inserted into the sleeve  133  of the upper case  120 . 
     In the state in which the coupling boss  175  is inserted into the sleeve  133 , a top surface of the coupling boss  175  may be disposed at the same height as a top surface of the sleeve  133  or disposed at a height lower than that of the top surface of the sleeve  133 . 
     A coupling member coupled to the coupling boss  175  may be, for example, a bolt (see reference symbol B 1  of  FIG. 3 ). The bolt B 1  may include a body part and a head part having a diameter greater than that of the body part. The bolt B 1  may be coupled to the coupling boss  175  from an upper side of the coupling boss  175 . 
     While the body part of the bolt B 1  is coupled to the coupling boss  175 , when the head part contacts the top surface of the sleeve  133 , and the head part contacts the top surface of the sleeve  133  and the top surface of the coupling boss  175 , assembling of the upper assembly  110  may be completed. 
     The upper support  170  may further include a plurality of unit guides  181  and  182  for guiding the connector  350  connected to the upper ejector  300 . 
     The plurality of unit guides  181  and  182  may be, for example, disposed to be spaced apart from each other in the direction of the arrow A with respect to  FIG. 13 . 
     The unit guides  181  and  182  may extend upward from the top surface of the support plate  171 . Each of the unit guides  181  and  182  may be connected to the circumferential wall  174 . 
     Each of the unit guides  181  and  182  may include a guide slot  183  vertically extends. 
     In a state in which both ends of the ejector body  310  of the upper ejector  300  pass through the guide slot  183 , the connector  350  is connected to the ejector body  310 . 
     Thus, when the rotation force is transmitted to the ejector body  310  by the connector  350  while the lower assembly  200  rotates, the ejector body  310  may vertically move along the guide slot  183 . 
     &lt;Upper Heater Coupling Structure&gt; 
       FIG. 14  is an enlarged view of a heater coupling part in the upper case of  FIG. 6B . 
     Referring to  FIG. 14 , the heater coupling part  124  may include a heater accommodation groove  124   a  accommodating the upper heater  148 . 
     For example, the heater accommodation groove  124   a  may be defined by recessing a portion of a bottom surface of the recess  122  of the upper case  120  upward. 
     The heater accommodation groove  124   a  may extend along a circumference of the tray opening  123  of the upper case  120 . 
     For example, the upper heater  148  may be a wire-type heater. Thus, the upper heater  148  may be bendable. The upper heater  148  may be bent to correspond to a shape of the heater accommodation groove  124   a  so as to accommodate the upper heater  148  in the heater accommodation groove  124   a.    
     The upper heater  148  may be a DC heater receiving DC power. The upper heater  148  may be turned on to transfer ice. 
     When heat of the upper heater  148  is transferred to the upper tray  150 , ice may be separated from a surface (inner face) of the upper tray  150 . 
     If the upper tray  150  is made of a metal material, and the heat of the upper heater  148  has a high temperature, a portion of the ice, which is heated by the upper heater  148 , may be adhered again to the surface of the upper tray after the upper heater  148  is turned off. As a result, the ice may be opaque. 
     That is, an opaque band having a shape corresponding to the upper heater may be formed around the ice. 
     However, in this embodiment, since the DC heater having low output is used, and the upper tray  150  is made of the silicon material, an amount of heat transferred to the upper tray  150  may be reduced, and thus, the upper tray itself may have low thermal conductivity. 
     Thus, the heat may not be concentrated into the local portion of the ice, and a small amount of heat may be slowly applied to prevent the opaque band from being formed around the ice because the ice is effectively separated from the upper tray. 
     The upper heater  148  may be disposed to surround the circumference of each of the plurality of upper chambers  152  so that the heat of the upper heater  148  is uniformly transferred to the plurality of upper chambers  152  of the upper tray  150 . 
     Also, the upper heater  148  may contact the circumference of each of the chamber walls  153  respectively defining the plurality of upper chambers  152 . Here, the upper heater  148  may be disposed at a position that is lower than that of the upper opening  154 . 
     Since the heater accommodation groove  124   a  is recessed from the recess  122 , the heater accommodation groove  124   a  may be defined by an outer wall  124   b  and an inner wall  124   c.    
     The upper heater  148  may have a diameter greater than that of the heater accommodation groove  124   a  so that the upper heater  148  protrudes to the outside of the heater coupling part  124  in the state in which the upper heater  148  is accommodated in the heater accommodation groove  124   a.    
     Since a portion of the upper heater  148  protrudes to the outside of the heater accommodation groove  124   a  in the state in which the upper heater  148  is accommodated in the heater accommodation groove  124   a , the upper heater  148  may contact the upper tray  150 . 
     A separation prevention protrusion  124   d  may be provided on one of the outer wall  124   b  and the inner wall  124   c  to prevent the upper heater  148  accommodated in the heater accommodation groove  124   a  from being separated from the heater accommodation groove  124   a.    
     In  FIG. 14 , for example, a plurality of separation prevention protrusions  124   d  are provided on the inner wall  124   c.    
     The separation prevention protrusion  124   d  may protrude from an end of the inner wall  124   c  toward the outer wall  124   b.    
     Here, a protruding length of the separation prevention protrusion  124   d  may be less than about ½ of a distance between the outer wall  124   b  and the inner wall  124   c  to prevent the upper heater  148  from being easily separated from the heater accommodation groove  124   a  without interfering with the insertion of the upper heater  148  by the separation prevention protrusion  124   d.    
     As illustrated in  FIG. 14 , in the state in which the upper heater  148  is accommodated in the heater accommodation groove  124   a , the upper heater  148  may be divided into an upper rounded portion  148   c  and an upper linear portion  148   d.    
     That is, the heater accommodation groove  124   a  may include an upper rounded portion and an upper linear portion. Thus, the upper heater  148  may be divided into the upper rounded portion  148   c  and the upper linear portion  148   d  to correspond to the upper rounded portion and the linear portion of the heater accommodation groove  124   a.    
     The upper rounded portion  148   c  may be a portion disposed along the circumference of the upper chamber  152  and also a portion that is bent to be rounded in a horizontal direction. 
     The liner portion  148   d  may be a portion connecting the upper rounded portions  148   c  corresponding to the upper chambers  152  to each other. 
     Since the upper heater  148  is disposed at a position lower than that of the upper opening  154 , a line connecting two points of the upper rounded portions, which are spaced apart from each other, to each other may pass through upper chamber  152 . 
     Since the upper rounded portion  148   c  of the upper heater  148  may be separated from the heater accommodation groove  124   a , the separation prevention protrusion  124   d  may be disposed to contact the upper rounded portion  148   c.    
       FIG. 15  is a cross-sectional view illustrating a state in which an upper assembly is assembled. 
     Referring to  FIGS. 3 and 15 , in the state in which the upper heater  148  is coupled to the heater coupling part  124  of the upper case  120 , the upper case  120 , the upper tray  150 , and the upper support  170  may be coupled to each other. 
     The first upper protrusion  165  of the upper tray  150  may be inserted into the first upper slot  131  of the upper case  120 . Also, the second upper protrusion  166  of the upper tray  150  may be inserted into the second upper slot  132  of the upper case  120 . 
     Then, the first lower protrusion  167  of the upper tray  150  may be inserted into the first lower slot  176  of the upper support  170 , and the second lower protrusion  168  of the upper tray  150  may be inserted into the second lower slot  177  of the upper support  170 . 
     Thus, the coupling boss  175  of the upper support  170  may pass through the through-hole of the upper tray  150  and then be accommodated in the sleeve  133  of the upper case  120 . In this state, the bolt B 1  may be coupled to the coupling boss  175  from an upper side of the coupling boss  175 . 
     In the state in which the bolt B 1  is coupled to the coupling boss  175 , the head part of the bolt B 1  may be disposed at a position higher than that of the upper plate  121 . 
     On the other hand, since the hinge supports  135  and  136  are disposed lower than the upper plate  121 , while the lower assembly  200  rotates, the upper assembly  110  or the connector  350  may be prevented from interfering with the head part of the bolt B 1 . 
     While the upper assembly  110  is assembled, a plurality of unit guides  181  and  182  of the upper support  170  may protrude upward from the upper plate  121  through the through-opening  139   b  and  139   c  defined in both sides of the upper plate  121 . 
     As described above, the upper ejector  300  passes through the guide slots  183  of the unit guides  181  and  182  protruding upward from the upper plate  121 . 
     Thus, the upper ejector  300  may descend in the state of being disposed above the upper plate  121  and be inserted into the upper chamber  152  to separate ice of the upper chamber  152  from the upper tray  150 . 
     When the upper assembly  110  is assembled, the heater coupling part  124  to which the upper heater  148  is coupled may be accommodated in the first accommodation part  160  of the upper tray  150 . 
     In the state in which the heater coupling part  124  is accommodated in the first accommodation part  160 , the upper heater  148  may contact the bottom surface  160   a  of the first accommodation part  160 . 
     Like this embodiment, when the upper heater  148  is accommodated in the heater coupling part  124  having the recessed shape to contact the upper tray body  151 , heat of the upper heater  148  may be minimally transferred to other portion except for the upper tray body  151 . 
     At least a portion of the upper heater  148  may be disposed to vertically overlap the upper chamber  152  so that the heat of the upper heater  148  is smoothly transferred to the upper chamber  152 . 
     In this embodiment, the upper rounded portion  148   c  of the upper heater  148  may vertically overlap the upper chamber  152 . 
     That is, a maximum distance between two points of the upper rounded portion  148   c , which are disposed at opposite sides with respect to the upper chamber  152  may be less than a diameter of the upper chamber  152 . 
     &lt;Lower Case&gt; 
       FIG. 16  is a perspective view of a lower assembly according to an embodiment.  FIG. 17  is an upper perspective view of a lower case according to an embodiment.  FIG. 18  is a lower perspective view of a lower case according to an embodiment. 
     Referring to  FIGS. 16 to 17 , the lower assembly  200  may include a lower tray  250 . The lower tray  250  defines the ice chamber  121  together with the upper tray  150 . 
     The lower assembly  200  may further include a lower support  270  that supports the lower tray  250 . The lower support  270  and the lower tray  250  may rotate together while the lower tray  250  is seated on the lower support  270 . 
     The lower assembly  200  may further include a lower case  210  for fixing a position of the lower tray  250 . 
     The lower case  210  may surround the circumference of the lower tray  250 , and the lower support  270  may support the lower tray  250 . 
     The connector  350  may be coupled to the lower support  270 . 
     The connector  350  may include a first link  352  that receives power of the driver  180  to allow the lower support  270  to rotate and a second link  356  connected to the lower support  270  to transmit rotation force of the lower support  270  to the upper ejector  300  when the lower support  270  rotates. 
     The first link  352  and the lower support  270  may be connected to each other by an elastic member  360 . For example, the elastic member  360  may be a coil spring. 
     The elastic member  360  may have one end connected to the first link  362  and the other end connected to the lower support  270 . 
     The elastic member  360  provides elastic force to the lower support  270  so that contact between the upper tray  150  and the lower tray  250  is maintained. 
     In this embodiment, the first link  352  and the second link  356  may be disposed on both sides of the lower support  270 , respectively. 
     One of the two first links may be connected to the driver  180  to receive the rotation force from the driver  180 . 
     The two first links  352  may be connected to each other by the connection shaft  370 . 
     A hole  358  through which the ejector body  310  of the upper ejector  300  passes may be defined in an upper end of the second link  356 . 
     The lower case  210  may include a lower plate  211  for fixing the lower tray  250 . 
     A portion of the lower tray  250  may be fixed to contact a bottom surface of the lower plate  211 . 
     An opening  212  through which a portion of the lower tray  250  passes may be defined in the lower plate  211 . 
     For example, when the lower tray  250  is fixed to the lower plate  211  in a state in which the lower tray  250  is disposed below the lower plate  211 , a portion of the lower tray  250  may protrude upward from the lower plate  211  through the opening  212 . 
     The lower case  210  may further include a circumferential wall  214  (or a cover wall) surrounding the lower tray  250  passing through the lower plate  211 . 
     The circumferential wall  214  may include a vertical wall  214   a  and a curved wall  215 . 
     The vertical wall  214   a  is a wall vertically extending upward from the lower plate  211 . The curved wall  215  is a wall that is rounded in a direction that is away from the opening  212  upward from the lower plate  211 . 
     The vertical wall  214   a  may include a first coupling slit  214   b  coupled to the lower tray  250 . The first coupling slit  214   b  may be defined by recessing an upper end of the vertical wall downward. 
     The curved wall  215  may include a second coupling slit  215   a  to the lower tray  250 . 
     The second coupling slit  215   a  may be defined by recessing an upper end of the curved wall  215  downward. 
     The lower case  210  may further include a first coupling boss  216  and a second coupling boss  217 . 
     The first coupling boss  216  may protrude downward from the bottom surface of the lower plate  211 . For example, the plurality of first coupling bosses  216  may protrude downward from the lower plate  211 . 
     The plurality of first coupling bosses  216  may be arranged to be spaced apart from each other in the direction of the arrow A with respect to  FIG. 17 . 
     The second coupling boss  217  may protrude downward from the bottom surface of the lower plate  211 . For example, the plurality of second coupling bosses  217  may protrude from the lower plate  211 . The plurality of first coupling bosses  217  may be arranged to be spaced apart from each other in the direction of the arrow A with respect to  FIG. 17 . 
     The first coupling boss  216  and the second coupling boss  217  may be disposed to be spaced apart from each other in the direction of the arrow B. 
     In this embodiment, a length of the first coupling boss  216  and a length of the second coupling boss  217  may be different from each other. For example, the first coupling boss  216  may have a length less than that of the second coupling boss  217 . 
     The first coupling member may be coupled to the first coupling boss  216  at an upper portion of the first coupling boss  216 . On the other hand, the second coupling member may be coupled to the second coupling boss  217  at a lower portion of the second coupling boss  217 . 
     A groove  215   b  for movement of the coupling member may be defined in the curved wall  215  to prevent the first coupling member from interfering with the curved wall  215  while the first coupling member is coupled to the first coupling boss  216 . 
     The lower case  210  may further include a slot  218  coupled to the lower tray  250 . 
     A portion of the lower tray  250  may be inserted into the slot  218 . The slot  218  may be disposed adjacent to the vertical wall  214   a.    
     For example, a plurality of slots  218  may be defined to be spaced apart from each other in the direction of the arrow A of  FIG. 17 . Each of the slots  218  may have a curved shape. 
     The lower case  210  may further include an accommodation groove  218   a  into which a portion of the lower tray  250  is inserted. 
     The accommodation groove  218   a  may be defined by recessing a portion of the lower tray  211  toward the curved wall  215 . 
     The lower case  210  may further include an extension wall  219  contacting a portion of the circumference of the side surface of the lower plate  212  in the state of being coupled to the lower tray  250 . The extension wall  219  may linearly extend in the direction of the arrow A. 
     &lt;Lower Tray&gt; 
       FIGS. 19 and 20  are perspective views of a lower tray viewed from above according to an embodiment.  FIG. 21  is a perspective view of a lower tray viewed from below according to an embodiment.  FIG. 22  is a plan view of a lower tray according to an embodiment.  FIG. 23  is a side view of a lower tray according to an embodiment. 
     Referring to  FIGS. 19 to 23 , the lower tray  250  may be made of a flexible material that is capable of being restored to its original shape after being deformed by an external force. 
     For example, the lower tray  250  may be made of a silicon material. Like this embodiment, when the lower tray  250  is made of a silicon material, the lower tray  250  may be restored to its original shape even through external force is applied to deform the lower tray  250  during the ice separating process. Thus, in spite of repetitive ice making, spherical ice may be made. 
     If the lower tray  250  is made of a metal material, when the external force is applied to the lower tray  250  to deform the lower tray  250  itself, the lower tray  250  may not be restored to its original shape any more. 
     In this case, after the lower tray  250  is deformed in shape, the spherical ice may not be made. That is, it is impossible to repeatedly make the spherical ice. 
     On the other hand, like this embodiment, when the lower tray  250  is made of the flexible material that is capable of being restored to its original shape, this limitation may be solved. 
     Also, when the lower tray  250  is made of the silicon material, the lower tray  250  may be prevented from being melted or thermally deformed by heat provided from an upper heater that will be described later. 
     The lower tray  250  may include a lower tray body  251  defining a lower chamber  252  that is a portion of the ice chamber  111 . 
     The lower tray body  251  may be defined by a plurality of lower chambers  252 . 
     For example, the plurality of lower chambers  252  may include a first lower chamber  252   a , a second lower chamber  252   b , and a third lower chamber  252   c.    
     The lower tray body  251  may include three chamber walls  252   d  defining three independent lower chambers  252   a ,  252   b , and  252   c . The three chamber walls  252   d  may be integrated in one body to form the lower tray body  251 . 
     In one example, the chamber wall  252   d  may have a hemispherical form. 
     The first lower chamber  252   a , the second lower chamber  252   b , and the third lower chamber  252   c  may be arranged in a line. For example, the first lower chamber  252   a , the second lower chamber  252   b , and the third lower chamber  252   c  may be arranged in a direction of an arrow A with respect to  FIG. 19 . 
     Accordingly, the lower chamber  252  may have a hemispherical shape or a shape similar to the hemispherical shape. That is, a lower portion of the spherical ice may be made by the lower chamber  252 . 
     In the specification, a similar shape to a hemisphere may refer to a shape approximately close to a hemisphere but not a complete hemisphere. 
     The lower tray  250  may further include a first extension part  253  horizontally extending from an edge of an upper end of the lower tray body  251 . The first extension part  253  may be continuously formed along the circumference of the lower tray body  251 . 
     The lower tray  250  may further include a circumferential wall  260  extended upward from an upper surface of the first extension part  253 . 
     A bottom surface of the upper tray body  151  may be contact with the top surface  251   e  of the lower tray body  251 . 
     The circumferential wall  260  may surround the upper tray body  251  seated on the top surface  251   e  of the lower tray body  251 . 
     The circumferential wall  260  may include a first wall  260   a  surrounding the vertical wall  153   a  of the upper tray body  151  and a second wall  260   b  surrounding the curved wall  153   b  of the upper tray body  151 . 
     The first wall  260   a  is a vertical wall vertically extending from the top surface of the first extension part  253 . The second wall  260   b  is a curved wall having a shape corresponding to that of the upper tray body  151 . That is, the second wall  260   b  may be rounded upward from the first extension part  253  in a direction that is away from the lower chamber  252 . 
     The lower tray  250  may further include a second extension part  254  horizontally extending from the circumferential wall  260 . 
     The second extension part  254  may be disposed higher than the first extension part  253 . Thus, the first extension part  253  and the second extension part  254  may be stepped with respect to each other. 
     The second extension part  254  may include a first upper protrusion  255  inserted into the slot  218  of the lower case  210 . The first upper protrusion  255  may be disposed to be horizontally spaced apart from the circumferential wall  260 . 
     For example, the first upper protrusion  255  may protrude upward from a top surface of the second extension part  254  at a position adjacent to the first wall  260   a.    
     Although not limited, a plurality of first upper protrusions  255  may be arranged to be spaced apart from each other in the direction of the arrow A with respect to  FIG. 20 . The first upper protrusion  255  may extend, for example, in a curved shape. 
     The second extension part  254  may include a first lower protrusion  257  inserted into a protrusion groove of the lower case  270 , which will be described later. The first lower protrusion  257  may protrude downward from a bottom surface of the second extension part  254 . 
     Although not limited, the plurality of first lower protrusions  257  may be arranged to be spaced apart from each other in the direction of arrow A. 
     The first upper protrusion  255  and the first lower protrusion  257  may be disposed at opposite sides with respect to a vertical direction of the second extension part  254 . At least a portion of the first upper protrusion  255  may vertically overlap the second lower protrusion  257 . 
     A plurality of through-holes may be defined in the second extension part  254 . 
     The plurality of through-holes  256  may include a first through-hole  256   a  through which the first coupling boss  216  of the lower case  210  passes and a second through-hole  256   b  through which the second coupling boss  217  of the lower case  210  passes. 
     For example, the plurality of through-holes  256   a  may be defined to be spaced apart from each other in the direction of the arrow A of  FIG. 19 . 
     Also, the plurality of second through-holes  256   b  may be disposed to be spaced apart from each other in the direction of the arrow A of  FIG. 19 . 
     The plurality of first through-holes  256   a  and the plurality of second through-holes  256   b  may be disposed at opposite sides with respect to the lower chamber  252 . 
     A portion of the plurality of second through-holes  256   b  may be defined between the two first upper protrusions  255 . Also, a portion of the plurality of second through-holes  256   b  may be defined between the two first lower protrusions  257 . 
     The second extension part  254  may further a second upper protrusion  258 . The second upper protrusion  258  may be disposed at an opposite side of the first upper protrusion  255  with respect to the lower chamber  252 . 
     The second upper protrusion  258  may be disposed to be horizontally spaced apart from the circumferential wall  260 . For example, the second upper protrusion  258  may protrude upward from a top surface of the second extension part  254  at a position adjacent to the second wall  260   b.    
     Although not limited, the plurality of second upper protrusions  258  may be arranged to be spaced apart from each other in the direction of the arrow A of  FIG. 19 . 
     The second upper protrusion  258  may be accommodated in the accommodation groove  218   a  of the lower case  210 . In the state in which the second upper protrusion  258  is accommodated in the accommodation groove  218   a , the second upper protrusion  258  may contact the curved wall  215  of the lower case  210 . 
     The circumferential wall  260  of the lower tray  250  may include a first coupling protrusion  262  coupled to the lower case  210 . 
     The first coupling protrusion  262  may horizontally protrude from the first wall  260   a  of the circumferential wall  260 . The first coupling protrusion  262  may be disposed on an upper portion of a side surface of the first wall  260   a.    
     The first coupling protrusion  262  may include a neck part  262   a  having a relatively less diameter when compared to those of other portions. The neck part  262   a  may be inserted into a first coupling slit  214   b  defined in the circumferential wall  214  of the lower case  210 . 
     The circumferential wall  260  of the lower tray  250  may further include a second coupling protrusion  262   c  coupled to the lower case  210 . 
     The second coupling protrusion  262   c  may horizontally protrude from the second wall  260   a  of the circumferential wall  260 . The second coupling protrusion  260   c  may be inserted into a second coupling slit  215   a  defined in the circumferential wall  214  of the lower case  210 . 
     The second coupling protrusion  260   c  may prevent an end of the second wall  260   b  of the lower tray  250  from contacting upper tray  150  and from being deformed during a procedure in which the lower tray  250  is rotated in an opposite direction. 
     When an end of the second wall  260   b  of the lower tray  250  contacts the upper tray  150  and is deformed, the lower tray  250  may be moved to a water supply position in the state in which the lower tray  250  enters the upper chamber  152  of the upper tray  150 . In this case, when ice is made after water is supplied, ice may not be formed in a sphere. 
     Thus, when the second coupling protrusion  260   c  protrudes from the second wall  260   b , the second wall  260   b  may be prevented from being deformed. Thus, the second coupling protrusion  260   c  may be referred to as an anti-deformation protrusion. 
     The second coupling protrusion  260   c  may protrude in a horizontal direction from the second wall  260   b.    
     An upper end of the second coupling protrusion  260   c  may be positioned at the same height as an upper end of the second wall  260   b.    
     The second coupling protrusion  260   c  may include a rounded surface  260   e  that is rounded downward from an upper side toward an external side in order to prevent the second coupling protrusion  260   c  from interfering with the upper tray  150  during a rotation procedure of the lower tray  250 . 
     A portion of a lower portion  260   d  of the second coupling protrusion  260   c  may be formed with a thickness that is reduced downward. The lower portion  260   d  of the second coupling protrusion  260   c  may be inserted into the second coupling slit  215   a.    
     The lower portion  260   d  of the second coupling protrusion  260   c  may be referred to as an insertion part. A lower surface of the insertion part may be a flat surface in such a way that the insertion part is stably positioned in the state in which the insertion part is inserted into the second coupling slit  215   a.    
     The lower portion  260   d  of the second coupling protrusion  260   c  may be spaced apart from the second extension part  254  of the lower tray  250  in such a way that the lower portion  260   d  of the second coupling protrusion  260   c  is inserted into the second coupling slit  215   a.    
     The second extension part  254  may include a second lower protrusion  266 . The second lower protrusion  266  may be disposed at an opposite side of the second lower protrusion  257  with respect to the lower chamber  252 . 
     The second lower protrusion  266  may protrude downward from a bottom surface of the second extension part  254 . For example, the second lower protrusion  266  may linearly extend. 
     A portion of the plurality of first through-holes  256   a  may be defined between the second lower protrusion  266  and the lower chamber  252 . 
     The second lower protrusion  266  may be accommodated in a guide groove defined in the lower support  270 , which will be described later. 
     The second extension part  254  may further a side restriction part  264 . The side restriction part  264  restricts horizontal movement of the lower tray  250  in the state in which the lower tray  250  is coupled to the lower case  210  and the lower support  270 . 
     The side restriction part  264  laterally protrudes from the second extension part  254  and has a vertical length greater than a thickness of the second extension part  254 . For example, one portion of the side restriction part  264  may be disposed higher than the top surface of the second extension part  254 , and the other portion of the side restriction part  264  may be disposed lower than the bottom surface of the second extension part  254 . 
     Thus, the one portion of the side restriction part  264  may contact a side surface of the lower case  210 , and the other portion may contact a side surface of the lower support  270 . In one example, the lower tray body  251  may has a heater contact portion  251   a  which the lower heater  296  contacts. In one example, the heater contact portion  251   a  may be formed on each of the chamber walls  252   d . The heater contact portion  251   a  may protrude from the respective chamber wall  252   d . In one example, the heater contact portion  251   a  may be formed in a circular ring shape. 
     The lower tray body  251  may further include the convex portion  251   b , a lower side of which is formed to be partially convex upward. That is, the convex portion  251   b  may be disposed to be convex toward an internal side of the ice chamber  111 . 
     &lt;Lower Support&gt; 
       FIG. 24  is a top perspective view of the lower support according to an embodiment,  FIG. 25  is a bottom perspective view of the lower support according to an embodiment, and  FIG. 26  is a cross-sectional view taken along  26 - 26  of  FIG. 16  for showing the state in which the lower assembly is assembled. 
     Referring to  FIGS. 24 to 26 , the lower support  270  may include a support body  271  supporting the lower tray  250 . 
     The support body  271  may include three chamber accommodation parts  272  accommodating the three chamber walls  252   d  of the lower tray  250 . The chamber accommodation part  272  may have a hemispherical shape. 
     The support body  271  may have a lower opening  274  through which the lower ejector  400  passes during the ice separating process. For example, three lower openings  274  may be defined to correspond to the three chamber accommodation parts  272  in the support body  271 . 
     A reinforcement rib  275  reinforcing strength may be disposed along a circumference of the lower opening  274 . 
     Also, the adjacent two accommodation part  272  of the three accommodation part  272  may be connected to each other by a connection rib  273 . The connection rib  273  may reinforce strength of the chamber wells  252   d.    
     The lower support  270  may further include a first extension wall  285  horizontally extending from an upper end of the support body  271 . 
     The lower support  270  may further include a second extension wall  286  that is formed to be stepped with respect to the first extension wall  285  on an edge of the first extension wall  285 . 
     A top surface of the second extension wall  286  may be disposed higher than the first extension wall  285 . 
     The first extension part  253  of the lower tray  250  may be seated on a top surface  271   a  of the support body  271 , and the second extension part  285  may surround side surface of the first extension part  253  of the lower tray  250 . Here, the second extension wall  286  may contact the side surface of the first extension part  253  of the lower tray  250 . 
     The lower support  270  may further include a protrusion groove  287  accommodating the first lower protrusion  257  of the lower tray  250 . 
     The protrusion groove  287  may extend in a curved shape. The protrusion groove  287  may be defined, for example, in a second extension wall  286 . 
     The lower support  270  may further include a first coupling groove  286   a  to which a first coupling member B 2  passing through the first coupling boss  216  of the upper case  210  is coupled. 
     The first coupling groove  286   a  may be provided, for example, in the second extension wall  286 . 
     The plurality of first coupling grooves  286   a  may be disposed to be spaced apart from each other in the direction of the arrow A in the second extension wall  286 . A portion of the plurality of first coupling grooves  286   a  may be defined between the adjacent two protrusion grooves  287 . 
     The lower support  270  may further include a boss through-hole  286   b  through which the second coupling boss  217  of the upper case  210  passes. 
     The boss through-hole  286   b  may be provided, for example, in the second extension wall  286 . A sleeve  286   c  surrounding the second coupling boss  217  passing through the boss through-hole  286   b  may be disposed on the second extension wall  286 . The sleeve  286   c  may have a cylindrical shape with an opened lower portion. 
     The first coupling member B 2  may be coupled to the first coupling groove  286   a  after passing through the first coupling boss  216  from an upper side of the lower case  210 . 
     The second coupling member B 3  may be coupled to the second coupling boss  217  from a lower side of the lower support  270 . 
     The sleeve  286   c  may have a lower end that is disposed at the same height as a lower end of the second coupling boss  217  or disposed at a height lower than that of the lower end of the second coupling boss  217 . 
     Thus, while the second coupling member B 3  is coupled, the head part of the second coupling member B 3  may contact bottom surfaces of the second coupling boss  217  and the sleeve  286   c  or may contact a bottom surface of the sleeve  286   c.    
     The lower support  270  may further include an outer wall  280  disposed to surround the lower tray body  251  in a state of being spaced outward from the outside of the lower tray body  251 . 
     The outer wall  280  may, for example, extend downward along an edge of the second extension wall  286 . 
     The lower support  270  may further include a plurality of hinge bodies  281  and  282  respectively connected to hinge supports  135  and  136  of the upper case  210 . 
     The plurality of hinge bodies  281  and  282  may be disposed to be spaced apart from each other in a direction of an arrow A of  FIG. 24 . Each of the hinge bodies  281  and  282  may further include a second hinge hole  281   a.    
     The shaft connection part  353  of the first link  352  may pass through the second hinge hole  281 . The connection shaft  370  may be connected to the shaft connection part  353 . 
     A distance between the plurality of hinge bodies  281  and  282  may be less than that between the plurality of hinge supports  135  and  136 . Thus, the plurality of hinge bodies  281  and  282  may be disposed between the plurality of hinge supports  135  and  136 . 
     The lower support  270  may further include a coupling shaft  283  to which the second link  356  is rotatably coupled. The coupling shaft  383  may be disposed on each of both surfaces of the outer wall  280 . 
     Also, the lower support  270  may further include an elastic member coupling part  284  to which the elastic member  360  is coupled. The elastic member coupling part  284  may define a space in which a portion of the elastic member  360  is accommodated. Since the elastic member  360  is accommodated in the elastic member coupling part  284  to prevent the elastic member  360  from interfering with the surrounding structure. 
     Also, the elastic member coupling part  284  may include a hook part  284   a  on which a lower end of the elastic member  370  is hooked. 
       FIG. 27  is a cross-sectional view taken along  27 - 27  of  FIG. 3 .  FIG. 28  is a view illustrating the state in which ice is completely made in  FIG. 27 . 
     Referring to  FIGS. 24 to 28 , a lower heater  296  may be mounted on the lower supporter  270 . 
     The lower heater  297  may provide the heat to the ice chamber  111  during the ice making process so that ice within the ice chamber  111  is frozen from an upper side. 
     Also, since lower heater  296  generates heat in the ice making process, bubbles within the ice chamber  111  may move downward during the ice making process. When the ice is completely made, a remaining portion of the spherical ice except for the lowermost portion of the ice may be transparent. According to this embodiment, the spherical ice that is substantially transparent may be made. 
     For example, the lower heater  296  may be a wire-type heater. 
     The lower heater  296  may be located between the lower tray  250  and the lower support  270 . 
     The lower heater  296  may be installed on the lower support  270 . Also, the lower heater  296  may contact the lower tray  250  to provide heat to the lower chamber  252 . 
     For example, the lower heater  296  may contact the lower tray body  251 . Also, the lower heater  296  may be disposed to surround the three chamber walls  252   d  of the lower tray body  251 . 
     In one example, the lower heater  296  may be in contact with the lower tray body  251 . The lower heater  296  may be arranged to surround the three chamber walls  252   d  of the lower tray body  251 . 
     The lower support  270  may include a heater accommodation groove  291  to be concave downward from the chamber accommodation part  272  of the lower tray body  251 . 
     The upper tray  150  and the lower tray  250  vertically contact each other to complete the ice chamber  111 . 
     The bottom surface  151   a  of the upper tray body  151  contacts the top surface  251   e  of the lower tray body  251 . 
     Here, in the state in which the top surface  251   e  of the lower tray body  251  contacts the bottom surface  151   a  of the upper tray body  151 , elastic force of the elastic member  360  is applied to the lower support  270 . 
     The elastic force of the elastic member  360  may be applied to the lower tray  250  by the lower support  270 , and thus, the top surface  251   e  of the lower tray body  251  may press the bottom surface  151   a  of the upper tray body  151 . 
     Thus, in the state in which the top surface  251   e  of the lower tray body  251  contacts the bottom surface  151   a  of the upper tray body  151 , the surfaces may be pressed with respect to each other to improve the adhesion. 
     As described above, when the adhesion between the top surface  251   e  of the lower tray body  251  and the bottom surface  151   a  of the upper tray increases, a gap between the two surface may not occur to prevent ice having a thin band shape along a circumference of the spherical ice from being made after the ice making is completed. 
     The first extension part  253  of the lower tray  250  is seated on the top surface  271   a  of the support body  271  of the lower support  270 . Also, the second extension wall  286  of the lower support  270  contacts a side surface of the first extension part  253  of the lower tray  250 . 
     The second extension part  254  of the lower tray  250  may be seated on the second extension wall  286  of the lower support  270 . 
     In the state in which the bottom surface  151   a  of the upper tray body  151  is seated on the top surface  251   e  of the lower tray body  251 , the upper tray body  151  may be accommodated in an inner space of the circumferential wall  260  of the lower tray  250 . 
     Here, the vertical wall  153   a  of the upper tray body  151  may be disposed to face the vertical wall  260   a  of the lower tray  250 , and the curved wall  153   b  of the upper tray body  151  may be disposed to face the second wall  260   b  of the lower tray  250 . 
     An outer face of the chamber wall  153  of the upper tray body  151  is spaced apart from an inner face of the circumferential wall  260  of the lower tray  250 . That is, a space may be defined between the outer face of the chamber wall  153  of the upper tray body  151  and the inner face of the circumferential wall  260  of the lower tray  250 . 
     Water supplied through the water supply part  180  is accommodated in the ice chamber  111 . When a relatively large amount of water than a volume of the ice chamber  111  is supplied, water that is not accommodated in the ice chamber  111  may flow into the space between the outer face of the chamber wall  153  of the upper tray body  151  and the inner face of the circumferential wall  260  of the lower tray  250 . 
     Thus, according to this embodiment, even though a relatively large amount of water than the volume of the ice chamber  111  is supplied, the water may be prevented from overflowing from the ice maker  100 . 
     In the state in which the top surface  251   e  of the lower tray body  251  contacts the bottom surface  151   a  of the upper tray body  151 , an upper surface of the circumferential wall  260  may be positioned higher than the upper chamber  152  or the upper opening  154  of the upper tray  150 . 
     A heater contact part  251   a  for allowing the contact area with the lower heater  296  to increase may be further provided on the lower tray body  251 . 
     The heater contact portion  251   a  may protrude from the bottom surface of the lower tray body  251 . In one example, the heater contact portion  251   a  may be formed in a ring shape and disposed on the bottom surface of the lower tray body  251 . The bottom surface of the heater contact portion  251   a  may be planar. 
     Without being limited to, the lower heater  296  may be positioned lower than an intermediate point of the height of the lower chamber  252  in the state in which the lower heater  296  contacts the heater contact portion  251   a.    
     The lower tray body  251  may further include a convex portion  251   b  in which a portion of the lower portion of the lower tray body  251  is convex upward. That is, the convex portion  251   b  may be convex toward the inside of the ice chamber  111 . 
     A recess  251   c  may be defined below the convex portion  251   b  so that the convex portion  251   b  has substantially the same thickness as the other portion of the lower tray body  251 . 
     In this specification, the “substantially the same” is a concept that includes completely the same shape and a shape that is not similar but there is little difference. 
     The convex portion  251   b  may be disposed to vertically face the lower opening  274  of the lower support  270 . 
     The lower opening  274  may be defined just below the lower chamber  252 . That is, the lower opening  274  may be defined just below the convex portion  251   b.    
     The convex portion  251   b  may have a diameter D less than that D 2  of the lower opening  274 . 
     When cold air is supplied to the ice chamber  111  in the state in which the water is supplied to the ice chamber  111 , the liquid water is phase-changed into solid ice. Here, the water may be expanded while the water is changed in phase. The expansive force of the water may be transmitted to each of the upper tray body  151  and the lower tray body  251 . 
     In case of this embodiment, although other portions of the lower tray body  251  are surrounded by the support body  271 , a portion (hereinafter, referred to as a “corresponding portion”) corresponding to the lower opening  274  of the support body  271  is not surrounded. 
     If the lower tray body  251  has a complete hemispherical shape, when the expansive force of the water is applied to the corresponding portion of the lower tray body  251  corresponding to the lower opening  274 , the corresponding portion of the lower tray body  251  is deformed toward the lower opening  274 . 
     In this case, although the water supplied to the ice chamber  111  exists in the spherical shape before the ice is made, the corresponding portion of the lower tray body  251  is deformed after the ice is made. Thus, additional ice having a projection shape may be made from the spherical ice by a space occurring by the deformation of the corresponding portion. 
     Thus, in this embodiment, the convex portion  251   b  may be disposed on the lower tray body  251  in consideration of the deformation of the lower tray body  251  so that the ice has the completely spherical shape. 
     In this embodiment, the water supplied to the ice chamber  111  is not formed into a spherical form before the ice is generated. After the generation of the ice is completed, the convex portion  251   b  of the lower tray body  251  is deformed toward the lower opening  274 , such that the spherical ice may be generated. 
     In the present embodiment, the diameter D 1  of the convex portion  251   b  is smaller than the diameter D 2  of the lower opening  274 , such that the convex portion  251   b  may be deformed and positioned inside the lower opening  274 . 
       FIG. 29  is a cross-sectional view taken along  29 - 29  of  FIG. 3  in the state in which water is supplied.  FIG. 30  is a cross-sectional view taken along  29 - 29  of  FIG. 3  in the state in which ice is made. 
       FIG. 31  is a cross-sectional view taken along  29 - 29  of  FIG. 2  in the state in which ice is completely made.  FIG. 32  is a cross-sectional view taken along  29 - 29  of  FIG. 3  in an early stage in which ice is transferred.  FIG. 33  is a cross-sectional view taken along  29 - 29  of  FIG. 3  at a position at which full ice is detected.  FIG. 34  is a cross-sectional view taken along  29 - 29  of  FIG. 3  at a position at which ice is completely transferred. 
     Referring to  FIGS. 29 to 34 , first, the lower assembly  200  rotates to a water supply position. 
     The top surface  251   e  of the lower tray  250  is spaced apart from the bottom surface  151   e  of the upper tray  150  at the water supply position of the lower assembly  200 . 
     Although not limited, the bottom surface  151   e  of the upper tray  150  may be disposed at a height that is equal or similar to a rotational center C 2  of the lower assembly  200 . 
     In this embodiment, the direction in which the lower assembly  200  rotates (in a counterclockwise direction in the drawing) is referred to as a forward direction, and the opposite direction (in a clockwise direction) is referred to as a reverse direction. 
     Although not limited, an angle between the top surface  251   e  of the lower tray  250  and the bottom surface  151   e  of the upper tray  150  at the water supply position of the lower assembly  200  may be about 8 degrees. 
     The detection body  710  may be positioned below the lower assembly  200  at a water supply position of the lower assembly  200 . 
     In this state, the water is guided by the water supply part  190  and supplied to the ice chamber  111 . 
     In this connection, the water is supplied to the ice chamber  111  through one upper opening of the plurality of upper openings  154  of the upper tray  150 . 
     In the state in which the supply of the water is completed, a portion of the supplied water may be fully filled into the lower chamber  252 , and the other portion of the supplied water may be fully filled into the space between the upper tray  150  and the lower tray  250 . 
     For example, the upper chamber  151  may have the same volume as that of the space between the upper tray  150  and the lower tray  250 . Thus, the water between the upper tray  150  and the lower tray  250  may be fully filled in the upper tray  150 . In another example, the volume of the upper chamber  152  may be smaller than the volume of the space between the upper tray  150  and the lower tray  250 . In this case, water may also be positioned in the upper chamber  152 . 
     In case of this embodiment, a channel for communication between the three lower chambers  252  may be provided in the lower tray  250 . 
     As described above, although the channel for the flow of the water is not provided in the lower tray  250 , since the top surface  251   e  of the lower tray  250  and the bottom surface  151   e  of the upper tray  150  are spaced apart from each other, the water may flow to the other lower chamber along the top surface  251   e  of the lower tray  250  when the water is fully filled in a specific lower chamber in the water supply process. 
     Thus, the water may be fully filled in each of the plurality of lower chambers  252  of the lower tray  250 . 
     In the case of this embodiment, since the channel for the communication between the lower chambers  252  is not provided in the lower tray  250 , additional ice having a projection shape around the ice after the ice making process may be prevented being made. 
     In the state in which the supply of the water is completed, as illustrated in  FIG. 30 , the lower assembly  200  rotates reversely. When the lower assembly  200  rotates reversely, the top surface  251   e  of the lower tray  250  is close to the bottom surface  151   e  of the upper tray  150 . 
     Thus, the water between the top surface  251   e  of the lower tray  250  and the bottom surface  151   e  of the upper tray  150  may be divided and distributed into the plurality of upper chambers  152 . 
     Also, when the top surface  251   e  of the lower tray  250  and the bottom surface  151   e  of the upper tray  150  are closely attached to each other, the water may be fully filled in the upper chamber  152 . 
     In the state in which the top surface  251   e  of the lower tray  250  and the bottom surface  151   e  of the upper tray  150  are closely attached to each other, a position of the lower assembly  200  may be called an ice making position. The detection body  710  may be positioned below the lower assembly  200  at a position of the lower assembly  200 , at which ice is made. 
     In the state in which the lower assembly  200  moves to the ice making position, ice making is started. 
     Since pressing force of water during ice making is less than the force for deforming the convex portion  251   b  of the lower tray  250 , the convex portion  251   b  may not be deformed to maintain its original shape. 
     When the ice making is started, the lower heater  296  is turned on. When the lower heater  296  is turned on, heat of the lower heater  296  is transferred to the lower tray  250 . 
     Thus, when the ice making is performed in the state where the lower heater  296  is turned on, ice may be made from the upper side in the ice chamber  111 . 
     According to the present embodiment, mass (or volume) of water per unit height may be constant or changed in the ice chamber  111  according to a shape of the ice chamber  111 . 
     For example, when the ice chamber  111  is shaped like a rectangle, mass (or volume) of water per unit height may be constant in the ice chamber  111 . 
     In contrast, when the ice chamber  111  has a shape of a circle, an inverted triangle, or a crescent moon, mass (or volume) of water per unit height may be changed. 
     Assuming that the temperature and amount of cool air supplied to the freezing compartment  4  are constant, when output of the lower heater  296  is constant, mass of water per unit height may be changed in the ice chamber  111 , and thus ice per unit height may be generated at different speeds. 
     For example, when mass of water per unit height is small, ice may be rapidly generated, but when mass of water per unit height is high, ice may be slowly generated. 
     As a result, a speed at which ice per unit height of water is not constant, and thus transparency of ice may be changed for each unit height. In particular, when ice is rapidly generated, bubbles do not move toward water from ice, and thus ice includes bubbles, thereby reducing transparency. 
     Thus, according to the present embodiment, output of the lower heater  296  may be controlled to be varied depending on mass of water per unit height in the ice chamber  111 . 
     Like in the present embodiment, for example, when the ice chamber  111  is formed like a sphere, mass of water per unit height in the ice chamber  111  may be increased to a maximum downward from an upper side and may be re-decreased. 
     Thus, after the lower heater  296  is turned on, output of the lower heater  296  may be sequentially reduced and may be minimized at a point when mass of water per unit height. Then, output of the lower heater  296  may be sequentially increased as mass of water per unit height is reduced. 
     Thus, ice is generated from an upper side in the ice chamber  111 , and thus bubbles in the ice chamber  111  may be moved downward. 
     In the process where ice is generated from a top to a bottom in the ice chamber  111 , the ice comes into contact with the top surface of the convex portion  251   b  of the lower tray  250 . 
     In this state, when the ice is continuously made, the block part  251   b  may be pressed and deformed as shown in  FIG. 31 , and the spherical ice may be made when the ice making is completed. 
     A control unit (not shown) may determine whether the ice making is completed based on the temperature sensed by the temperature sensor  500 . 
     The lower heater  296  may be turned off at the ice-making completion or before the ice-making completion. 
     When the ice-making is completed, the upper heater  148  is first turned on for the ice-removal of the ice. When the upper heater  148  is turned on, the heat of the upper heater  148  is transferred to the upper tray  150 , and thus, the ice may be separated from the surface (the inner face) of the upper tray  150 . 
     After the upper heater  148  has been activated for a set time duration, the upper heater  148  may be turned off and then the drive unit  180  may be operated to rotate the lower assembly  200  in a forward direction. 
     As illustrated in  FIG. 32 , when the lower assembly  200  rotates forward, the lower tray  250  may be spaced apart from the upper tray  150 . 
     Also, the rotation force of the lower assembly  200  may be transmitted to the upper ejector  300  by the connector  350 . Thus, the upper ejector  300  descends by the unit guides  181  and  182 , and the upper ejecting pin  320  may be inserted into the upper chamber  152  through the upper opening  154 . 
     In the ice separating process, the ice may be separated from the upper tray  250  before the upper ejecting pin  320  presses the ice. That is, the ice may be separated from the surface of the upper tray  150  by the heat of the upper heater  148 . 
     In this case, the ice may rotate together with the lower assembly  200  in the state of being supported by the lower tray  250 . 
     Alternatively, even though the heat of the upper heater  148  is applied to the upper tray  150 , the ice may not be separated from the surface of the upper tray  150 . 
     Thus, when the lower assembly  200  rotates forward, the ice may be separated from the lower tray  250  in the state in which the ice is closely attached to the upper tray  150 . 
     In this state, while the lower assembly  200  rotates, the upper ejecting pin  320  passing through the upper opening  154  may press the ice closely attached to the upper tray  150  to separate the ice from the upper tray  150 . The ice separated from the upper tray  150  may be supported again by the lower tray  250 . 
     When the ice rotates together with the lower assembly  200  in the state in which the ice is supported by the lower tray  250 , even though external force is not applied to the lower tray  250 , the ice may be separated from the lower tray  250  by the self-weight thereof. 
     Like in  FIG. 33 , during a procedure in which the lower assembly  200  is moved at the correct position, the full ice detection lever  700  may be moved to a full ice detection position. In this case, when the ice bin  102  is not filled with ice, the full ice detection lever  700  may be moved to the full ice detection position. 
     In the state in which the full ice detection lever  700  is moved to the full ice detection position, the full ice detection lever  700  may be positioned below the lower assembly  200 . 
     While the lower assembly  200  rotates, even though the ice is not separated from the lower tray  250  by the self-weight thereof, when the lower tray  250  is pressed by the lower ejector  400  as shown in  FIG. 34 , the ice may be separated from the lower tray  250 . 
     Particularly, while the lower assembly  200  rotates, the lower tray  250  may contact the lower ejecting pin  420 . 
     When the lower assembly  200  continuously rotates forward, the lower ejecting pin  420  may press the lower tray  250  to deform the lower tray  250 , and the pressing force of the lower ejecting pin  420  may be transmitted to the ice to separate the ice from the lower tray  250 . The ice separated from the surface of the lower tray  250  may drop downward and be stored in the ice bin  102 . 
     After the ice is separated from the lower tray  250 , the lower assembly  200  may be rotated in the reverse direction by the drive unit  180 . 
     When the lower ejecting pin  420  is spaced apart from the lower tray  250  in a process in which the lower assembly  200  is rotated in the reverse direction, the deformed lower tray  250  may be restored to its original form. 
     In the reverse rotation process of the lower assembly  200 , the rotational force is transmitted to the upper ejector  300  by the connecting unit  350 , such that the upper ejector  300  is raised, and thus, the upper ejecting pin  320  is removed from the upper chamber  152 . 
     When the lower assembly  200  reaches the water supply position, the drive unit  180  is stopped, and then water supply starts again. 
     According to the proposed embodiment, cool air passing through a cool air hole may be concentrated into an upper side of an ice chamber by a cool air guide, and thus a plurality of ices may be generated at uniform speeds and may be maintained in a spherical shape, thereby preventing completely made ices from being connected to each other. 
     According to the present embodiment, a speed at which ice is generated may be delayed by a lower heater for supplying heat to an ice chamber, and bubbles may be moved toward water from a portion at which ice is generated, and accordingly, transparent ice may be advantageously made. 
     According to the present embodiment, irrespective of a type of a refrigerator including an ice maker installed therein, cool air passing through the cool air hole may flow, and thus a flowing pattern of the cool air may be almost constant. Thus, the transparency of ice may be advantageously uniform irrespective of a type of the refrigerator. 
     According to the present embodiment, a side wall including a driver installed thereon for rotating a lower tray may be prevented from being deformed, and thus the driver and the lower assembly may be prevented from being separated from each other during a procedure in which the lower tray repeatedly reciprocates. 
     According to the present embodiment, a lower tray may include an anti-deformation protrusion, and thus may be prevented from being deformed by interference with the upper tray during a rotation procedure of the lower tray, and accordingly, ice may be prevented from being made with a non-spherical shape in a next procedure of making ice.