Abstract:
Disclosed is a refrigerator comprising a main body formed with at least one cooling chamber and an evaporator, and a cool air duct forming a cool air path guiding cool air from the evaporator into the fresh food compartment, the refrigerator further comprising a damper plate rotatably installed in the cool air duct, opening and closing the cool air path; a damper driving motor rotating the damper plate; a temperature sensor sensing an inner temperature of the cooling chamber; and a controller controlling the damper driving motor so as to open and close the damper plate, based on an open degree of the damper plate predetermined according to the inner temperature sensed by the temperature sensor. With this configuration, there are provided a refrigerator efficiently controlling the inner temperature of the cooling chamber and a method for controlling the same.

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from my applications entitled Refrigerator And Control Method Thereof filed with the Korean Industrial Property Office on Feb. 9, 2000 and there duly assigned Ser. No. 2000-6040 and filed with the Korean Industrial Property Office on Oct. 5, 2000 and there duly assigned Ser. No. 2000-58578. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a refrigerator and a method for controlling the same. 
     2. Description of the Related Art 
     Referring to FIG. 1 which is a side sectional view of a refrigerator, the refrigerator is comprised of a main body  1  formed with a fresh food compartment  3  and a freezer compartment  5 , and doors  7  and  9  installed in front of the main body  1 , opening and closing the fresh food compartment  3  and the freezer compartment  5 . In the rear lower part of the main body  1  is provided a component chamber  30  accommodating therein a compressor  31  compressing a refrigerant and a condenser (not shown). 
     In the rear of the freezer component  5  are provided an evaporator  15  generating cool air by means of the refrigerant from the compressor  31  and an evaporator accommodating part  10  accommodating the evaporator  15  therein. 
     The evaporator accommodating part  10  includes a rear cover  11  and a front cover  13 . The rear cover  11  is spaced from the rear wall of the freezer compartment  5  at a predetermined interval and the front cover  13  is spaced from the rear cover  11  at a predetermined interval, having cool air discharge holes. On the rear lower part of the rear cover  11  is provided a supporter  12  supporting the evaporator  15 . Above the upper part of the evaporator  15  is installed a fan  17  blowing the cool air generated from the evaporator  15  into the freezer compartment  5 . 
     In the rear of the inner wall of the main body  1  are provided a cool air duct  40  and a cool air circulation duct  43 . The cool air duct  40  includes a cool air path  41  guiding the cool air generated from the evaporator  15  into the fresh food compartment  3 , and the cool air circulation duct  43  guides the air passing through the fresh food compartment  3  toward the evaporator  15 . The cool air duct  40  extends toward the rear wall of the fresh food compartment  3  from the evaporator accommodating part  10  positioned in the rear of the freezer compartment  5 , and the cool air circulation duct  43  extends toward the evaporator  15  from the rear lower part of the fresh food compartment  3 . 
     In the cool air duct  40  is installed a damper  150  opening and closing the cool air path  41  so as to control an inner temperature of the fresh food compartment  3 . In the fresh food compartment  3  is installed a temperature sensor  20  sensing the inner temperature of the fresh food compartment  3 . In the main body  1  is provided a controller (not shown) controlling an operation of the damper  150  so as to allow the damper  150  to open and close the cool air path  41  according to the inner temperature of the fresh food compartment  3 , the temperature being sensed by the temperature sensor  20 . 
     FIG. 2 is a sectional view taken along line—of FIG. 1, showing the conventional damper  150 . As shown therein, the conventional cool air duct  40  is comprised of a cool air hole communicating with the cool air path  41 . The conventional damper  150  is comprised of a damper plate  151  opening and closing the cool air hole  42 , and a driving means  153  installed in one end of the damper plate  151 , adjusting opening and closing of the damper plate  151 . The driving means  153  is comprised of a solenoid having a plunger (not shown). Between the damper plate  151  and the driving means  143  is provided an elastic plate  154 . One end of the elastic plate  154  is installed in the damper plate  151  and the other end thereof is installed in the plunger (not shown). 
     When the refrigerator starts to operate, the temperature sensor  20  senses an inner temperature of the fresh food compartment  3 . If the sensed inner temperature of the fresh food compartment  3  is higher than a predetermined temperature, the controller drives the driving means  153  to wholly open the cool air path  41 . If the cool air path  41  is entirely opened, the cool air generated from the evaporator  15  is supplied into the fresh food compartment  3  through the cool air path  41 , to thereby decrease the inner temperature of the fresh food compartment  3  so as not to exceed the predetermined temperature. 
     If the sensed inner temperature of the fresh food compartment  3  is not higher than the predetermined temperature, the controller activates the driving means  153  to wholly close the cool air path  41 . If the cool air path  41  is entirely closed, the cool air from the evaporator  15  cannot be supplied into the fresh food compartment  3 , to thereby allow the inner temperature thereof not to be lower than the predetermined temperature. 
     In the conventional refrigerator, the damper plate is structured simply to wholly open and close the cool air path of the cool air duct, so that it is difficult to appropriately adjust the amount of the cool air supplied into the cooling chamber according to the inner temperature of the cooling chamber, thereby being unable to effectively control the inner temperature of the cooling chamber. 
     SUMMARY OF THE INVENTION 
     The present invention has been made keeping in mind the above-described problem, and an object of the present invention is to provide a refrigerator capable of efficiently controlling an inner temperature of a cooling chamber, and a method for controlling the temperature. 
     This and other objects of the present invention may be achieved by a provision of a refrigerator comprising a main body formed with at least one cooling chamber and an evaporator, and a cool air duct forming a cool air path guiding cool air from the evaporator into the cooling chamber, further comprising a damper plate rotatably installed in the cool air duct, opening and closing the cool air path; a damper driving motor rotating the damper plate; a temperature sensor sensing an inner temperature of the cooling chamber; and a controller controlling the damper driving motor so as to open and close the damper plate, based on an open degree of the damper plate predetermined according to the inner temperature sensed by the temperature sensor. 
     The damper driving motor is installed outside the cool air duct, and the damper plate is of substantially rectangular and planar shape, corresponding to a sectional shape of the cool air duct, and it is installed inside the cool air path, and is rotatably coupled to a rotational shaft of the damper driving motor. 
     The refrigerator further comprises a damper rotation sensing part having a magnet coupled to a rotational shaft of the damper driving motor, generating a rotation signal, and a damper rotation speed sensor installed adjacent to the rotational shaft, sensing the rotation speed of the rotational shaft of the damper driving motor by means of the rotation signal from the magnet. 
     The damper rotation sensing part senses the open degree of the damper plate by means of the rotation speed detected by the rotation speed sensor and rotation time of the damper driving motor. 
     The controller controls the damper driving motor so as to allow the damper plate to have an open degree appropriate for the sensed inner temperature, by comparing the open degree of the damper plate sensed by the damper rotation sensing part and the predetermined open degree of the damper plate. 
     The controller controls the rotation time of the damper driving motor so as to adjust the open degree of the damper plate. 
     According to another aspect of the present invention, this and other objects may be achieved by a provision of a method for controlling a refrigerator comprising a main body formed with at least one cooling chamber and an evaporator, a cool air duct forming a cool air path guiding cool air from the evaporator into the cooling chamber, a damper plate rotatably installed in the cool air duct, opening and closing the cool air path, and a damper driving motor rotating the damper plate, comprising the steps of sensing the inner temperature of the cooling chamber to predetermine an open degree of the damper plate according to a sensed inner temperature; sensing the open degree of the damper plate; comparing the open degree of the damper plate predetermined according to the inner temperature and the sensed open degree of the damper plate; and controlling the damper driving motor so as to open the damper plate with the predetermined open degree. 
     In the step of sensing the open degree of the damper plate, rotation time of the damper driving motor is sensed, to determine the open degree of the damper plate. 
     In the step of controlling the damper driving motor, rotation time of the damper driving motor is controlled. 
     This and other objects of the present invention may also be achieved by a provision of a refrigerator comprising a main body formed with at least one cooling chamber and an evaporator, and a cool air duct forming a cool air path guiding cool air from the evaporator into the fresh food compartment, further comprising a damper plate rotatably installed in the cool air duct, opening and closing the cool air path; a damper driving motor rotating the damper plate; a frequency detector detecting the frequency of power supplied to the damper driving motor; a temperature sensor sensing an inner temperature of the cooling chamber; and a controller controlling power supply to the damper driving motor according to an open degree of the damper plate predetermined based on the sensed inner temperature and a power supply time set up based on the detected frequency. 
     The refrigerator further comprises a damper rotation sensing part having a magnet coupled to a rotational shaft of the damper driving motor, generating a rotation signal, and a damper rotation speed sensor installed adjacent to the rotational shaft, sensing the rotation speed of the rotational shaft of the damper driving motor by means of the rotational signal from the magnet. 
     The frequency detector detects the frequency of the power based on the rotation speed of the damper plate sensed by the damper rotation sensing part. 
     The controller determines a wholly opened point and a wholly closed point of the damper plate, based on the rotation speed of the damper plate sensed by the damper rotation sensing part, and controls the open degree of the damper plate according to the sensed inner temperature. 
     This and other objects of the present invention may also be achieved by a provision of a method for controlling a refrigerator comprising a main body formed with at least one cooling chamber and an evaporator, a cool air duct forming a cool air path guiding cool air from the evaporator into the cooling chamber, a damper plate rotatably installed in the cool air duct, opening and closing the cool air path, and a damper driving motor rotating the damper plate with power supply, comprising the steps of detecting the frequency of the power supply to the damper driving motor; sensing an inner temperature of the cooling chamber; and determining an open degree of the damper plate based on the sensed inner temperature, determining power supply time based on the open degree and the detected frequency, and supplying the power to the damper driving motor for the determined power supply time. 
     In the step of detecting the frequency, the frequency of the power supply is determined based on a rotation speed of the damper driving motor detected by dividing the rotation angle of the damper plate by the power supply time to the damper driving motor. 
     In the step of determining the open degree of the damper plate, the controller determines a wholly opened point and a wholly closed point of the damper plate based on a rotation degree of the damper plate sensed by a damper rotation sensing part and the detected frequency of the power supply. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
     FIG. 1 is a side sectional view of a refrigerator; 
     FIG. 2 is a sectional view taken along line—of FIG. 1, showing a damper installed in a conventional refrigerator; 
     FIG. 3 is a sectional view taken along line—of FIG. 1, showing a damper installed in a refrigerator according to the present invention; 
     FIG. 4 is a block diagram showing a temperature control of a refrigerator according to a first embodiment of the present invention; 
     FIG. 5 is a flow chart illustrating a method for controlling a temperature of the refrigerator of FIG. 4; 
     FIG. 6 is a block diagram showing a temperature control of a refrigerator according to a second embodiment of the present invention; 
     FIG. 7 is a flow chart illustrating a method for controlling a temperature of the refrigerator of FIG. 6; and 
     FIG. 8 is a graph showing the relation of the open degree of a damper plate and a temperature of the refrigerator according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 3 and 4, a refrigerator according to a first embodiment of the present invention is comprised of a damper  50  opening and closing a cool air path  41  of a cool air duct  40 , which is activated by means of an external power, a temperature sensor  20  (see FIG. 4) installed in a fresh food compartment  3  (see FIG.  1 ), sensing an inner temperature of the fresh food compartment  3 , and a controller  80  controlling driving of the damper  50  based on the temperature of the fresh food compartment  3  sensed by the temperature sensor  20 . 
     The damper  50  is comprised of a damper plate  51  rotatably installed in the cool air duct  40 , a damper driving motor  53  rotating the damper plate  51 , and a damper rotation sensor  60  sensing rotation of the damper plate  51 . The damper plate  51  is substantially of planar shape, corresponding to a sectional shape of the cool air duct  40 , being coupled to a rotational shaft  55  of the damper driving motor  53  installed outside the cool air duct  40 . 
     The damper rotation sensor  60  is comprised of a magnet  61  and a speed sensor  63 . The magnet  61  is coupled to the rotational shaft  55  of the damper driving motor  53 , generating rotation signals according to the rotation of the damper driving motor  53 , and the speed sensor  63  is installed adjacent to the rotational shaft  55  of the damper driving motor  53 , sensing a rotation speed of the rotational shaft  55  of the damper driving motor  53  by means of the rotational signal from the magnet  61 . 
     The damper rotation sensor  60  senses the open degree of the damper plate  51  according to the rotation time of the damper driving motor  53 . The process of sensing the open degree of the damper plate  51  is conducted in the following manner: 
     The speed sensor  63  senses the rotation speed of the damper driving motor  53  based on the rotation signal from the magnet  61 , and determines the open degree of the damper plate  51  by detecting the rotation time of the damper driving motor  53  according to the sensed rotation speed. 
     For example, where the rotation speed of the damper driving motor  53  is 6 rpm, that is, the damper driving motor  53  is rotated with 360° for 10 seconds, if the rotation time of the damper driving motor  53  is 2.5 seconds, the damper plate  51  is rotated with 90°, allowing the cool air path  25  to maintain the wholly opened state. If the rotation time of the damper driving motor  53  is 5 seconds, the damper plate  51  is rotated with 180°, allowing the cool air path  41  to maintain the wholly closed state. 
     If the damper driving motor  53  is rotated for 7.5 seconds, the damper plate  51  is rotated with 270°, allowing the cool air path  41  to maintain the wholly opened state. If the damper driving motor  53  is rotated for 10 seconds, the damper plate  51  is rotated with 360°, allowing the cool air path  41  to maintain the wholly closed state. 
     As shown in FIG. 4, the controller  80  compares the open degree of the damper plate  51  sensed by the damper rotation sensor  60  and the open degree of the damper plate  51  predetermined according to the temperature of the fresh food compartment  3  sensed by the temperature sensor  20 , and controls the damper driving motor  53  so that the open degree of the damper plate  51  conforms with the predetermined open degree thereof. 
     Hereinafter, a process of setting up an open degree of the damper plate  51  according to an inner temperature of the fresh food compartment  3  sensed by the temperature sensor  20  will be described. 
     First, the point when a sensed temperature is the set up minimum temperature of the fresh food compartment  3  is set up a wholly closed point of the damper plate  51 , and the point when a sensed temperature is the set up maximum temperature of the fresh food compartment  3  is set up a wholly opened point of the damper plate  51 . The temperature difference section between the set up minimum temperature and the set up maximum temperature and the displacement difference section between the wholly closed point and the wholly opened point of the damper plate  51  are uniformly divided into a plurality of sections of the same number. The open degree of the damper plate  51  is set up according to the temperature sections and the displacement sections. 
     For example, if the set up minimum temperature of the fresh food compartment  3  is 1 and the set up maximum temperature thereof is 6, the damper plate  51  entirely closes the cool air path  41  at 1, and entirely opens the cool air path  41  at 6. If the temperature difference section between the set up minimum temperature and the set up maximum temperature is divided into five sections of 1˜2, 2˜3, 3˜4, 4˜5 and 5˜6, and the displacement difference section between the wholly closed section and the wholly opened section of the damper plate  51  are divided into five sections, the open degree of the damper plate  51  can be predetermined. 
     The controller  80  compares the open degree of the damper plate  51  sensed by the damper rotation sensor  60  (hereinafter, referred to as “a sensed open degree”) and the open degree of the damper plate predetermined according to an inner temperature of the fresh food compartment  3  sensed by the temperature sensor  20  (hereinafter, referred to as “a set up open degree”) to determine whether they are identical to each other. If the sensed open degree and the set up open degree are identical, the controller  80  does not activate the damper driving motor  53 . If both open degrees are not identical, the controller  80  rotates the damper driving motor  53  so as to allow the damper plate  53  to have the setup open degree. The controller  80  controls the rotation time of the damper driving motor  53  so as to allow the damper plate  53  to have the set up open degree. 
     For example, if the respective temperatures of the set up minimum temperature and the set up maximum temperature of the fresh food compartment  3  are 1 and 6, the controller  80  can control supply time of power to the damper driving motor  53  by dividing 2.5 seconds, the time which is taken to wholly close the damper plate  41 , into five sections. 
     If the inner temperature of the fresh food compartment raises by 1 when the inner temperature of the fresh food compartment  3  is the set up minimum temperature and the damper plate  51  is at the wholly closed point, the controller  80  can control the open degree of the damper plate  51  by opening the damper plate  51  by 18° for 0.5 seconds in view of the power supply time. 
     Referring to FIG. 5, the controller  80  first rotates the damper driving motor  53  by 360° several times and then stops to operate the damper driving motor  53  (S 01 ). The damper rotation sensor  60  senses the rotation speed of the damper driving motor  53  (S 02 ), and the open degree of the damper plate  51  is determined based on the sensed rotation speed (S 03 ). 
     For example, if it takes 10 seconds from the time when a rotation signal from the magnet  61  is sensed by the speed sensor  63 , when the damper driving motor  53  is rotated, to the time when the rotation signal is sensed again by the speed sensor  63 , and it takes 2.5 seconds from the time when the final rotation signal of the magnet  61  is sensed, to the time when the damper driving motor  53  stops to operate, the damper rotation sensor  60  can detect that the rotation speed of the damper driving motor  53  is 6 rpm and the damper plate  51  is at the wholly opened point. 
     The rotation speed of the damper driving motor  53  and the open degree of the damper plate  51  as sensed are transmitted to the controller  80 , along with the inner temperature of the fresh food compartment  3  sensed by the temperature sensor  20  (S 04 ). The controller  80  compares the sensed open degree of the damper plate  51  and the set up open degree of the damper plate  51  to determine whether they are identical (S 05 ). If the set up open degree and the sensed open degree are identical, the controller does not operate the damper driving motor  53  so as to maintain the current open degree. If the set open degree and the sensed open degree are not identical, the controller rotates the damper driving motor  53  so as to make the sensed open degree and the set up open degree of the damper plate  51  identical (S 07 ). 
     Referring to FIG. 8, the relation between the sensed open degree of the damper plate  51  employed in the refrigerator according to the present invention and the temperature of the fresh food compartment  3  sensed by the temperature sensor  20  will be described below. As shown therein, when the inner temperature of the fresh food compartment  3  is higher than the set up minimum temperature or lower than the set up maximum temperature, the controller  80  controls the rotation time of the damper driving motor  53  to allow the open degree of the damper plate  51  to increase or decrease, so that the damper plate  51  has the set up open degree according to the temperature of the fresh food compartment  3 . In response to decrease or increase in the open degree, the amount of air supplied to the fresh food compartment  3  adaptively decreases or increases, thereby adjusting the amount of air supply according to the inner temperature of the fresh food compartment  3 , and further efficiently controlling the inner temperature of the fresh food compartment  3 . 
     Referring to FIG. 6, a refrigerator according to a second embodiment of the present invention is comprised of a temperature sensor  20  sensing an inner temperature of the fresh food compartment  3  (see FIG.  1 ), and a frequency detector  70  detecting the frequency of the power supplied to the damper driving motor  53 . The refrigerator is further comprised of a controller  80  setting up the open degree of the damper plate  51  based on the inner temperature of the fresh food compartment sensed by the temperature sensor  20 , and controlling the damper driving motor  53  based on the set up open degree and the frequency detected by the frequency detector  70 . 
     The frequency detector  70  detects the rotation speed of the damper driving motor  54  by dividing the rotational angle of the damper plate  51  sensed by the damper rotation sensor  60  into the power supply time to the damper driving motor  53 , and detects the frequency of the power supplied based on the detected value. 
     For example, if it takes  10  seconds from the point when the rotation signal from the magnet  61  is sensed by the speed sensor  63  to the point when the signal is re-sensed after being rotated with 360°, the rotation speed of the damper plate  51  is 6 rpm. If the rotation speed of the damper plate  51  is 6 rpm, the frequency detector  70  detects the power supply of  60 . If it takes 12 seconds from the point when the rotation signal from the magnet  61  is sensed by the speed sensor  63  to the point when the signal is re-sensed after being rotated with 360°, that is, if the rotation speed of the damper plate  51  is 5 rpm, the frequency detector  70  detects the power supply of  50 . 
     If power is supplied to the damper driving motor  53  for 2.5 seconds or 7.5 seconds when the frequency of power supply detected in the frequency detector  70  is  60  , the controller  80  rotates the damper plate  51  so as to be at the wholly opened point. If power is supplied to the damper driving motor  53  for 0 second, 5 seconds and 10 seconds, the controller  80  rotates the damper plate  51  at the wholly closed point. 
     If power is supplied to the damper driving motor  53  for 3 seconds or 9 seconds when the power of 50 is supplied, the damper plate  51  is rotated so as to be at the wholly opened point. If power is supplied to the damper driving motor  53  for 0 second, 6 seconds and 12 seconds, the damper plate  51  is rotated at the wholly closed point. 
     The controller  80  determines the open degree of the damper plate  51  based on the inner temperature of the fresh food compartment  3  sensed by the temperature sensor  20  and supplies the power to the damper driving motor  53  according to the power supply time set up based on the open degree of the damper plate  51  and the frequency detected by the frequency detector  70 , thereby controlling the rotation of the damper plate  51 . 
     Referring to FIG. 7, the method for controlling a temperature of a refrigerator shown in FIG. 6 will be described below. As shown, if the refrigerator starts to operate according to the second embodiment of the present invention, the controller  80  first rotates the damper driving motor  53  by 360° several times (S 101 ). The damper rotation sensor  60  senses the rotation speed of the damper driving motor  53  (S 102 ). 
     The frequency detector  70  detects the frequency of the power supplied to the damper driving motor  53  based on the rotation speed sensed by the damper rotation sensor  60  (S 103 ), and determines whether the detected frequency is 60 or 50 (S 104 ). In other words, if it takes 10 seconds for the damper driving motor  53  to make one revolution (the rotation speed is 6 rpm), the frequency detector  70  determines that the detected frequency of the power supply is 60. If it takes 12 seconds for the damper driving motor  53  to make one revolution (the rotation speed is 5 rpm), the frequency detector  70  determines that the detected frequency of the power supply is  50 . If the frequency is determined to be  60  , the temperature sensor  20  senses the inner temperature of the fresh food compartment  3  and transmits the sensed temperature to the controller  80  (S 105 ). Then, the controller  80  compares to determine whether the inner temperature of the refrigerator sensed by the temperature sensor  20  higher or lower than the predetermined temperature (S 106 ). If the inner temperature of the fresh food compartment  3  is higher than the predetermined temperature, the controller  80  supplies the power to the damper driving motor  53  for 2.5 seconds or 7.5 seconds from the point when the rotational signal from the magnet  61  is sensed, thereby wholly opening the damper plate  51  (S 107 ). If the sensed inner temperature of the fresh food compartment in the step S 106  is determined to be lower than the predetermined temperature, the controller  80  supplies the power to the damper driving motor  53  for 5 seconds from the point when the rotational signal from the magnet  61  is sensed, thereby wholly closing the damper plate  51  (S 108 ). 
     If the frequency of the power supply detected by the frequency detector  70  is determined to be 50, the inner temperature of the fresh food compartment  3  is sensed and transmitted to the controller  80  as in the step S 105  (S 109 ). It is determined whether the inner temperature of the fresh food compartment  3  sensed by the temperature sensor  20  is higher or lower than the predetermined temperature (S 110 ). If the inner temperature of the fresh food compartment  3  is higher than the predetermined temperature, the controller  80  supplies the power to the damper driving motor  53  for 3 seconds or 9 seconds from the point when the rotational signal from the magnet  61  is sensed, thereby wholly opening the damper plate  51  (S 111 ). If the sensed inner temperature of the fresh food compartment in the step S 106  is determined to be lower than the predetermined temperature, the controller  80  supplies the power to the damper driving motor  53  for 6 seconds from the point when the rotational signal from the magnet  61  is sensed, thereby wholly closing the damper plate  51  (S 112 ). 
     Accordingly, although the frequency of the power supply varies, the open degree of the damper plate  51  can be efficiently adjusted, thereby being able to maintain the temperature of the fresh food compartment at an optimum state. 
     With this configuration, the inner temperature of the cooling chamber can be efficiently adjusted by adjusting the open degree of the damper plate according to the inner temperature of the cooling chamber and controlling the damper driving motor according to the frequency of the power supply. 
     According to the present invention, a refrigerator efficiently controlling the inner temperature of the cooling chamber, and a method for controlling the same are provided. Additionally, a refrigerator capable of adjusting the open degree of the damper plate according to the inner temperature of the cooling chamber and the frequency of the power supply, and a method for controlling the same are provided. 
     Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, modifications, substitutions and deletions not specifically described may be made without departing from the spirit and scope of the invention as defined in the appended claims.