Abstract:
A damper cleaning apparatus for a two compartment refrigerator having a damper for controlling airflow between compartments. The damper cleaning apparatus includes a damper drive mechanism for opening and closing the damper. A controller for controlling the damper drive mechanism repeats a cleaning operation at a set interval. The cleaning operation includes plural repetitions of at least partially opening the damper and then at least partially closing the damper. Optionally, the controller waits for the defrosting apparatus to be turned off and then subsequently performs the cleaning operation.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     The present application claims the benefit of U.S. patent application Ser. No. 10/643,388 filed Aug. 19, 2003, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to automatic defrost controls for two compartment refrigerators, and more particularly to automatic defrost controllers including air damper control.  
         [0003]     Refrigerators having two refrigeration compartments, including a fresh food compartment and a frozen food compartment, are well known. Many of these two compartment refrigerators have refrigeration apparatus connected to the frozen food compartment and a duct for carrying cool air from the frozen food compartment to the fresh food compartment. In order to regulate the temperature of the fresh food compartment, a damper or baffle is often provided within or adjacent to the duct. The baffle is thermostatically controlled to provide a desired temperature within the fresh food compartment.  
         [0004]     Self defrosting refrigerators generally include a defrost heater for melting ice that has accumulated on the refrigeration apparatus. However, the operation of the defrost heater will often cause water to accumulate on or near the air duct damper. Subsequently, especially when the cooling apparatus is operated, the water can freeze and form ice that interferes with the effective operation of the damper.  
         [0005]     In order to avoid this problem, a number of solution has been proposed. In U.S. Pat. No. 5,201,888 to Beach et al. a control moves the damper to a fully closed position while energizing the defrost heater. Thus, the formation of condensation and subsequent ice formation is reduced. However, water can still accumulate on the baffle, which later freezes, especially when the defrost heater must be operated for an extended period of time.  
         [0006]     U.S. Pat. No. 5,375,413 to Fredell et al. discloses a two-element sliding air baffle for a refrigerator. The second baffle element is operated by a solenoid that, in a closed position, is periodically pulsed (every one minute) thereby exerting a repeated rocking or leveraging motion on the second baffle member. The rocking motion enhances the break up of any ice that has formed between the two baffle elements. However, once ice has formed, it can be very difficult to remove.  
         [0007]     Further, energy conservation is becoming more and more important in appliances such as refrigerators. Although many energy saving measures have been developed, there are significant inefficiencies in the operation of such refrigerators.  
         [0008]     Thus, there is a need for a refrigerator capable of preventing the build-up of ice on an air duct damper. Further, there is a need for improving the energy efficiency of refrigerators.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009]     The present invention provides a damper cleaning apparatus for a two compartment refrigerator having a damper for controlling airflow between compartments. The damper cleaning apparatus comprises a damper drive mechanism for opening and closing the damper; and a controller for controlling the damper drive mechanism wherein the controller repeats a cleaning operation at a set interval. The cleaning operation comprises plural repetitions of at least partially opening the damper and then at least partially closing the damper.  
         [0010]     According to another aspect, the present invention provides a two compartment refrigerator having a damper for controlling airflow between compartments. The refrigerator comprises a damper drive mechanism for opening and closing the damper; a controller for controlling the damper drive mechanism, wherein the controller performs a cleaning operation by at least partially opening the damper and then at least partially closing the damper; and a defrosting apparatus. The controller waits for the defrosting apparatus to be turned off and then subsequently performs the cleaning operation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0011]      FIG. 1  schematically shows a refrigerator according to an embodiment of the present invention; and  
         [0012]      FIG. 2  shows a flow diagram for the operation of a automatic defrost controller according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     As shown in  FIG. 1 , the present embodiment of the invention provides an automatic defrost controller (ADC) that controls the operation of a defrost heater in a refrigerator  10  having a cabinet  11 . The ADC also controls the operation of a defrosting apparatus or defrost heater  12 , an evaporator fan  14  and a air damper  16  positioned in an air duct  18  located in a divider wall  20  separating a frozen food compartment  22  and a fresh food compartment  24  of the refrigerator  10 . A refrigeration apparatus  25 , including a compressor, condenser and evaporator (not separately shown), is controlled by a freezer control or thermostat  26  to maintain the frozen food compartment  22  at a set temperature. A fresh food control or thermostat  28  maintains the fresh food compartment  24  at a set temperature by controlling the opening and closing of the damper  16  and the operation of the evaporator fan  14  to provide cooling air from the frozen food compartment  22  through the air duct  18 . The defrost heater  12  is located adjacent to a portion of the refrigeration apparatus, i.e. the evaporator, on which ice forms in order to remove the ice.  
         [0014]     As shown in  FIG. 2 , the ADC according to the present embodiment controls the operation of the defrost heater  12  and the other components of the refrigerator as follows. The ADC control flow commences at step S 1  when power is provided to the ADC.  
         [0015]     At step S 2 , if the freezer control  26  indicates that no cooling is needed in the frozen food compartment  22  (the compressor is off) control passes to step S 3 . At step S 3 , if the ADC determines from a door sensor or switch  30  that the refrigerator door  32  has not been opened for a predetermined number of previous refrigeration cycles or compressor on/off cycles, such as one or three cycles, then the ADC returns to step S 2 . Otherwise, if the door  32  was opened during the last three cycles, then control passes to step S 4 .  
         [0016]     At step S 4 , if the fresh food control  28  is not calling for cooling then the ADC turns off the evaporator fan  14  at step S 5 , closes the damper  16  at step S 6  and returns to step S 2 . Otherwise, if the fresh food control calls for cooling at step S 4 , the ADC opens the damper at step S 7 , runs the evaporator fan at step S 8  and returns to step S 2 .  
         [0017]     If, at step S 2 , the freezer control  26 is calling for cooling, control passes to step S 9 . At step S 9 , if the defrost relay is not set to defrost, control passes to step Si  0  where the ADC pauses for a fan delay time to allow the compressor time to begin providing cooling air. Next, at step S 11 , the ADC initiates a damper cleaning operation, as describe below in more detail, and then passes to step S 12  to run the evaporator fan and then pass to step S 13 .  
         [0018]     At step S 13 , if the freezer control no longer requires cooling (the compressor has stopped), the evaporator fan is turned off at step S 17 . Next at step S 18 , if the cumulative compressor run time is greater than or equal to a set defrost interval, X, then the defrost relay is set to defrost at step S 19  and control returns to step S 2 . Otherwise, control returns directly to step S 2 .  
         [0019]     At step S 9 , if the defrost relay is set to defrost, control passes to step S 20 . At step S 20 , the evaporator fan is turned off, the damper is closed at step S 21 , and the defrost heater is energized at step S 22 . Next, at step S 23 , the defrost heater remains energized until a defrost termination thermostat opens in response to reaching a set temperature, indicating that the melting of the frost on the evaporator is complete, at which time control passes to step S 24  and the defrost heater is turned off. ADC control then returns to step S 2 .  
         [0020]     As described above and shown in the drawing figure at reference number  110 , the ADC turns off the evaporator fan and closes the damper during the operation of the defrost heater. This helps to prevent moisture from collecting on the damper that would subsequently turn into ice and interfere with the operation of the damper.  
         [0021]     In order to prevent water that may have accumulated during defrosting from freezing on or near the damper, the ADC periodically performs a damper cleaning operation S 11  as described above. During this damper cleaning operation S 11 , the ADC causes the damper door to open and close a specified number of times at a specified frequency. This movement of the damper causes accumulated water on and near the damper to be removed. As shown in the drawing figure at reference number  112 , the damper cleaning operation S 11  is initiated just prior to the operation of the evaporator fan S 12 . In the present embodiment, during the damper cleaning operation, the damper is repeatedly moved to a fully open position and then to a fully closed position. It is contemplated to be within the scope of the present invention that the damper may alternatively be moved to a partially open position and/or a partially closed position during the damper cleaning cycle. The time between openings and closings can be set to any appropriate amount, such as 1 or 2 seconds. Alternatively, the damper can be opened and closed in immediate succession without any delay. The number of open/close cycles can be set to any appropriate amount, such as one or two or more. Alternatively, the number of open/close cycles and/or their timing can be controlled in a closed-loop fashion, such as based on the length of the prior defrost cycle.  
         [0022]     Further, the ADC monitors a door switch to determine when the door of the fresh food compartment has been opened. If the compressor goes through a set number of refrigeration cycles or “on/off” cycles, without the door being opened, the damper is kept closed during subsequent compressor “off” cycles. This prevents migration of cold air from the freezer compartment to the fresh food compartment when no cooling has been called for by the freezer control. As shown in the drawing figure at reference number  114 , this is accomplished in the present embodiment by bypassing the off-cycle damper control routine  116  when the door has not been opened in the three prior refrigeration cycles S 3 . It should be appreciated that the number three has been used as an example, and that the number of cycles can be set to any appropriate number, including one, two, four or more. Further, different intervals, other than refrigeration cycles, to determine when to allow the damper to be opened when the compressor is off.  
         [0023]     It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.