Patent Publication Number: US-2005115250-A1

Title: Refrigerator

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims the benefit of Korean Patent Application No. 2003-0086943, filed Dec. 02, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a refrigerator, and, more particularly, to a refrigerator in which internal temperature is maintained within a predetermined range even though external temperature fluctuates.  
      2. Description of the Related Art  
      Generally, a refrigerator includes a load-driving unit to lower and raise an internal temperature thereof, an internal temperature sensor to sense the internal temperature, and a controller to store a preset temperature range to set the internal temperature, to compare the preset temperature range with a sensed internal temperature that is sensed by the internal temperature sensor, and to control the load-driving unit so as to maintain the internal temperature within the preset temperature range.  
      With this configuration, the refrigerator is controlled as follows.  
      First, the internal temperature sensor transmits information about the sensed internal temperature to the controller. Then, the controller compares the previously stored preset temperature range with the internal temperature sensed by the internal temperature sensor. Where the sensed internal temperature is higher than the upper limit of the preset temperature range, the controller controls the load-driving unit to be turned on/off so as to lower the internal temperature. Oppositely, in the case where the sensed internal temperature is lower than the lower limit of the preset temperature range, the controller controls the load-driving unit to be turned on/off so as to raise the internal temperature.  
      However, in the conventional refrigerator, the internal temperature of the refrigerator is controlled on the basis of the sensed internal temperature regardless of the external temperature. Thus, the fact that an external temperature affects the internal thermostatic performance of the refrigerator is not considered. In other words, when the external temperature of the refrigerator is low, the internal temperature is lowered, and when the external temperature of the refrigerator is high, the internal temperature is increased, and as a result, the thermostatic performance of the refrigerator is deteriorated.  
      Accordingly, a refrigerator including an external temperature sensor to sense an external temperature, and a controller which sets variable widths of the preset temperature range respectively corresponding to a plurality of deviating steps that are divided according to the extent that the sensed external temperature is beyond the preset temperature range and which changes the limit of the preset temperature range by the variable width corresponding to the deviating step according to the sensed external temperature has been proposed. Such a construction controls a load-driving unit based on a result of comparing the changed preset temperature range with internal temperature that is sensed by an internal temperature sensor. However, the internal thermostatic performance of this conventional refrigerator deteriorates when the sensed external temperature fluctuates at a boundary between the steps.  
      For example, referring to  FIG. 1 , the external temperature sensed by the external temperature sensor goes over the preset temperature range and the external temperature is maintained in a B-step between temperatures T 2  and T 3 . At this time, the controller changes the limit of the preset temperature range by the variable width corresponding to the B-step and thus controls the load-driving unit. Then, at a time t 1 , the external temperature range is changed to an A-step between temperatures T 1  and T 2 . From the time t 1 , the controller changes the limit of the preset temperature range by the variable width corresponding to the A-step and thus controls the load-driving unit. Then, at a time t 2 , the external temperature range is changed to the B-step. From the time t 2 , the controller changes the limit of the preset temperature range by the variable width corresponding to the B-step and thus controls the load-driving unit. Then, at a time t 3 , the external temperature range is changed to the A-step. From the time t 3 , the controller changes the limit of the preset temperature range by the variable width corresponding to the A-step and thus controls the load-driving unit.  
      When the sensed external temperature fluctuates at the boundary between the A-step and the B-step, the controller has to frequently change the preset temperature range and control the load-driving unit to be turned on/off depending on the changed preset temperature range. This phenomenon causes the internal thermostatic performance of the refrigerator to deteriorate.  
     SUMMARY OF THE INVENTION  
      Accordingly, an aspect of the present invention provides a refrigerator in which internal temperature is maintained within a predetermined range even though external temperature fluctuates.  
      The foregoing and/or other aspects of the present invention are also achieved by providing a refrigerator with a load-driving unit to lower or raise internal temperature thereof, the refrigerator comprising an external temperature sensor to sense external temperature; an internal temperature sensor to sense the internal temperature; and a controller to change at least one of upper and lower limits of a preset temperature range by a preset width and to control the load-driving unit on the basis of the internal temperature sensed by the internal temperature sensor when the external temperature that is sensed by the external temperature sensor goes over a predetermined level beyond the upper or lower limits of the preset temperature range and is then maintained over a predetermined period of time.  
      According to another aspect of the invention, the controller controls the load-driving unit such that a plurality of deviating steps is set according to the extent that the sensed external temperature is beyond the preset temperature range, variable widths of the preset temperature range are respectively set corresponding to the plurality of deviating steps, and such that the limit of the preset temperature range, by a predetermined variable width, corresponds to the deviating step according to the external temperature sensed by the external temperature sensor.  
      According to another aspect of the invention, the limit of the preset temperature range is changed in a direction, which is reverse to a change direction of the external temperature sensed by the external temperature sensor corresponding to the predetermined temperature.  
      According to another aspect of the invention, the load-driving unit comprises a cold generator to lower the internal temperature, and a heat generator to raise the internal temperature.  
      Additional and/or other aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
       FIG. 1  is a graph showing a sensed external temperature so as to control a conventional refrigerator;  
       FIG. 2  is a control block diagram of a refrigerator according to an embodiment of the present invention;  
       FIG. 3  is a control flowchart of the refrigerator according to an embodiment of the present invention; and  
       FIG. 4  is a graph showing a sensed external temperature so as to control the refrigerator according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.  
       FIG. 2  is a control block diagram of a refrigerator according to an embodiment of the present invention. As shown therein, a refrigerator according to an embodiment of the present invention comprises a load-driving unit  30  to lower and raise an internal temperature of the refrigerator; an external temperature sensor  50  to sense an external temperature of the refrigerator; an internal temperature sensor  40  to sense the internal temperature of the refrigerator; and a controller  60  to change a limit of a preset temperature range by a predetermined width when the external temperature sensed by the external temperature sensor  50  exceeds a predetermined level beyond the limit of the preset temperature range and is then maintained in excess of the predetermined level beyond a predetermined period of time, so as to control the load-driving unit  30  based on a result of a comparison between the changed preset temperature range and the internal temperature sensed by the internal temperature sensor  40 .  
      The load-driving unit  30  comprises a compressor  20  that is driven to generate a cold temperature so as to lower the internal temperature, and a heater  10  that is driven to generate heat so as to raise the internal temperature.  
      The compressor  20  is employed as a cooling device that is driven to lower the internal temperature by compressing a refrigerant into high-temperature and high-pressure refrigerant gas. Thus, the refrigerator comprises the compressor  20 , a condenser (not shown) to cool the refrigerant from the compressor  20  by exchanging heat with ambient air, and an evaporator (not shown) to evaporate the refrigerant from the condenser (not shown) into low-temperature and low-pressure refrigerator, so as to lower the internal temperature of a food storage compartment.  
      The controller  60  sets a plurality of deviating steps that are divided according to the extent that the sensed external temperature exceeds the preset temperature range, and sets variable widths of the preset temperature range respectively corresponding to the plurality of deviating steps so as to optimize the internal temperature.  
      When the external temperature sensed by the external temperature sensor  50  exceeds the preset temperature range and then is maintained in the predetermined deviating step among the plurality of deviating steps during a predetermined period of time, the controller  60  changes the limit of the preset temperature range by a predetermined width that corresponds to the deviating step, according to the sensed external temperature, in a direction which is reverse to a changing direction of the external temperature that is sensed by the external temperature sensor corresponding to the predetermined temperature. As a result, the compressor  20  and the heater  10  are turned on/off on the basis of a sensed internal temperature of the internal temperature sensor  40 .  
      With this configuration, controls of the refrigerator according to an embodiment of the present invention will be described with reference to  FIG. 3 .  
      At operation  100 , the controller  60  sets a plurality of deviating steps that are divided according to the extent that the sensed external temperature exceeds the preset temperature range, and sets variable widths of the preset temperature range respectively corresponding to the plurality of deviating steps. At operation  110 , the external temperature sensor  50  senses the external temperature of the refrigerator and transmits information about the sensed external temperature to the controller  60 . At operation  120 , the internal temperature sensor  40  senses the internal temperature of the refrigerator and transmits information about the sensed internal temperature to the controller  60 . At operation  130 , the controller  60  determines whether the external temperature sensed by the external temperature sensor  50  is maintained within a predetermined deviating step among the plurality of deviating steps during a predetermined period of time. Where the external temperature is maintained within a predetermined deviating step during a predetermined period of time, at operation  140 , the controller  60  changes the limit of the preset temperature range by a predetermined width corresponding to the deviating step, so as to control the compressor  20  or the heater  10  to be turned on/off.  
      For example, when the external temperature sensed by the external temperature sensor  50  fluctuates as shown in  FIG. 4 , control of the refrigerator is as follows. Referring to  FIG. 4 , the external temperature sensed after a time t 1 ′ is not maintained for a period of time t within an A′-step; the external temperature sensed after a time t 2 ′ is not maintained for the period of time t within a B′-step; and the external temperature sensed after a time t 3 ′ is maintained for the period of time t within the A-step. In this case, the controller  60  changes the limit of the preset temperature range by the variable width corresponding to the B′-step, so as to control the compressor  20  or the heater  10  to be turned on/off based on the sensed internal temperature of the internal temperature sensor  40 . Further, the controller  60  determines that the external temperature sensed after the time t 3 ′ is maintained over the period of time t within the A′-step, and changes the limit of the preset temperature range by the variable width corresponding to the A′-step after a time t 3 ′+t, thereby controlling the compressor  20  or the heater  10  to be turned on/off.  
      Similarly, when the external temperature of the refrigerator fluctuates at a boundary between the A′-step and the B′-step, the limit of the preset temperature range is changed by the variable width corresponding to the A′-step or the B′-step within which the external temperature is maintained over the period of time t, so as to control the compressor  20  and the heater  10  to be turned on/off. Thus, even though the external temperature fluctuates, the internal temperature is effectively maintained within a preset temperature range.  
      Here,  FIGS. 2 and 3  illustrate a Kimchi refrigerator by way of example, which is easily affected by the external temperature. In the case of a general home refrigerator comprising a refrigerating compartment and a freezing compartment, the load-driving unit further comprises a fan motor to effectively maintain the internal temperature by the control method according to the present invention.  
      Further, the period of time t is set in consideration of the external temperature of the refrigerator so as to maintain the internal temperature of the refrigerator within an optimized preset temperature range.  
      As is described above, the present invention provides a refrigerator in which internal temperature is maintained within a predetermined range even though external temperature fluctuates.  
      Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.