Patent Application
20050039472
The present invention relates to automatic defrost controls for two compartment refrigerators, and more particularly to automatic defrost controllers including air damper control.
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.
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.
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.
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.
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.
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.
According to a first aspect, the present invention provides a refrigerator comprising a cabinet; a first refrigerated compartment within the cabinet having a door; a second refrigerated compartment within the cabinet; a dividing wall separating the first refrigerated compartment from the second refrigerated compartment; a duct connecting the first refrigerated compartment for airflow communication with the second refrigerated compartment; a damper movable between an open position and a closed position for controlling airflow within the duct; a refrigeration apparatus having a refrigeration cycle being measured from a first starting of the refrigeration apparatus to a second consecutive starting of the refrigeration apparatus, and an off cycle being a time within said refrigeration cycle during which the refrigeration apparatus is not operating; a controller for controlling the damper; and a door sensor connected to the controller for detecting when the door is open. If the controller determines that the door has remained closed for a set number of refrigeration cycles, the controller maintains the damper in the closed position during a subsequent consecutive off cycle.
According to a second aspect, the present invention provides a self defrosting refrigerator comprising: a cabinet; a first refrigerated compartment within the cabinet having a first door; a second refrigerated compartment within the cabinet having a second door; a dividing wall separating the first refrigerated compartment from the second refrigerated compartment; a duct connecting the first refrigerated compartment for airflow communication with the second refrigerated compartment; a damper movable between an open position and a closed position for controlling airflow within the duct; a refrigeration apparatus within the cabinet; and a controller for controlling the damper. The controller carries out a damper cleaning operation in which the controller at least partially opens and then at least partially closes the damper a set number of times at a set interval.
As shown in
As shown in
At step S2, 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 S3. At step S3, 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 S2. Otherwise, if the door 32 was opened during the last three cycles, then control passes to step S4.
At step S4, if the fresh food control 28 is not calling for cooling then the ADC turns off the evaporator fan 14 at step S5, closes the damper 16 at step S6 and returns to step S2. Otherwise, if the fresh food control calls for cooling at step S4, the ADC opens the damper at step S7, runs the evaporator fan at step S8 and returns to step S2.
If, at step S2, the freezer control 26 is calling for cooling, control passes to step S9. At step S9, if the defrost relay is not set to defrost, control passes to step S10 where the ADC pauses for a fan delay time to allow the compressor time to begin providing cooling air. Next, at step S11, the ADC initiates a damper cleaning operation, as describe below in more detail, and then passes to step S12 to run the evaporator fan and then pass to step S13.
At step S13, if the freezer control no longer requires cooling (the compressor has stopped), the evaporator fan is turned off at step S17. Next at step S18, 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 S19 and control returns to step S2. Otherwise, control returns directly to step S2.
At step S9, if the defrost relay is set to defrost, control passes to step S20. At step S20, the evaporator fan is turned off, the damper is closed at step S21, and the defrost heater is energized at step S22. Next, at step S23, 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 S24 and the defrost heater is turned off. ADC control then returns to step S2.
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.
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 S11 as described above. During this damper cleaning operation S11, 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 S11 is initiated just prior to the operation of the evaporator fan S12. 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.
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 S3. 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.
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.
