Patent Document

BACKGROUND OF THE INVENTION 
     This invention relates generally to sealed system refrigeration devices, and more particularly, to control systems for refrigerators. 
     Typical refrigerators includes a fresh food compartment and a frozen food compartment. A temperature sensor is typically located in walls of both compartments and sends indications of the sensors temperature to a control unit which controls a compressor and a plurality of fans for cooling the compartments. 
     However, the temperature of the sensor is not typically the same as the temperature of the air within each compartment. Rather the wall in which the sensor is mounted effects the temperature of the sensor. For example, if a sensor in the fresh food compartment is mounted in a mullion which is a common wall between the fresh food compartment and the frozen food compartment, the sensor is at a temperature cooler than the air within the fresh food compartment. Alternatively, if a sensor is mounted in an exterior wall, then the sensor is typically warmer than the air within the fresh food compartment. Both of these two phenomenons are attributable to heat transfer through the wall in which the sensor is mounted. Therefore, the temperature sent to the control unit can vary from the true temperature of the air within a compartment. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, a method for controlling a cooling system configured to cool a compartment is provided. The method includes receiving a temperature of the compartment from a temperature sensor, adjusting the received temperature to obtain a corrected temperature, and controlling the cooling system based on the corrected temperature. 
     In another aspect, a cooling device includes a first compartment comprising a plurality of first walls and at least one first door defining a first enclosed volume of the first compartment. A sealed system configured to provide cooling capacity to the first compartment is operationally coupled to the first compartment and at least one first temperature sensor is coupled to at least one of the first walls and at least partially exposed to the first enclosed volume. A temperature control system is operationally coupled to said the temperature sensor and to the sealed system. The control system is configured to receive a temperature sensor reading from the first temperature sensor, and to control a temperature of the first compartment with the sealed system based on the temperature sensor reading and a correction factor. 
     In a further aspect, a refrigerator includes a first compartment configured to preserve food, the first compartment includes a plurality of first walls and at least one first door defining a first enclosed volume of the first compartment. The refrigerator also includes a second compartment configured to preserve food coupled to one of the first walls, the second compartment includes a plurality of second walls and at least one second door defining a second enclosed volume of the second compartment with one of the first walls. A sealed system is operationally coupled to the first and second compartments. The sealed system is configured to provide cooling capacity to the first and second compartments. At least one first temperature sensor is coupled to at least one of the first walls and at least partially exposed to the first enclosed volume. A temperature control system is operationally coupled to the first temperature sensor and to the sealed system. The control system is configured to receive a temperature sensor reading from the first temperature sensor, and to control a temperature of the first compartment with the sealed system based on the temperature sensor reading and a correction factor. 
     In yet another embodiment, a refrigerator includes a first compartment configured to preserve food, the first compartment includes a plurality of first walls and at least one first door defining a first enclosed volume of the first compartment. The refrigerator also includes a second compartment configured to preserve food coupled to one of the first walls, the second compartment includes a plurality of second walls and at least one second door defining a second enclosed volume of the second compartment with one of the first walls. A sealed system is operationally coupled to the first and second compartments, and the sealed system is configured to provide cooling capacity to the first and second compartments. At least one first temperature sensor is coupled to at least one of the first walls and at least partially exposed to the first enclosed volume. At least one second temperature sensor is at least partially exposed to the second enclosed volume. A temperature control system is operationally coupled to the first and second temperature sensors and to the sealed system. The control system is configured to receive a first temperature sensor reading from the first temperature sensor and receive a second temperature sensor reading from the second temperature sensor. The control system is also configured to control a first temperature of the first compartment with the sealed system based on the first temperature sensor and a correction factor that is a function of temperature difference between the first received temperature sensor reading and the second received temperature sensor reading. The control system is also configured to control a second temperature of the second compartment with the sealed system based on the second temperature sensor and a correction factor that is a function of temperature difference between the first received temperature sensor reading and the second received temperature sensor reading, wherein the second temperature is different from said first temperature. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an exemplary refrigerator. 
     FIG. 2 illustrates test data of the refrigerator shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a side-by-side refrigerator  100  in which the present invention may be practiced. It is recognized, however, that the benefits of the present invention apply to other types of refrigerators, freezers, refrigeration appliances, and refrigeration devices, including climate control systems having similar control issues and considerations such as, for example, but not limited to, one compartment units, three compartment units, units with any number of compartments, commercial units including vending units, and residential units. Consequently, the description set forth herein is for illustrative purposes only and is not intended to limit the invention in any aspect. 
     Refrigerator  100  includes a fresh food storage compartment  102  and a freezer storage compartment  104 . Freezer compartment  104  and fresh food compartment  102  are arranged side-by-side in an outer case  106  with inner liners  108  and  110 . A space between case  106  and liners  108  and  110 , and between liners  108  and  110 , is filled with foamed-in-place insulation. Outer case  106  normally is formed by folding a sheet of a suitable material, such as pre-painted steel, into an inverted U-shape to form top and side walls of case. A bottom wall of case  106  normally is formed separately and attached to the case side walls and to a bottom frame that provides support for refrigerator  100 . 
     Inner liners  108  and  110  are molded from a suitable plastic material to form freezer compartment  104  and fresh food compartment  102 , respectively. Alternatively, liners  108 ,  110  may be formed by bending and welding a sheet of a suitable metal, such as steel. The illustrative embodiment includes two separate liners  108 ,  110  as it is a relatively large capacity unit and separate liners add strength and are easier to maintain within manufacturing tolerances. In smaller refrigerators, a single liner is formed and a mullion spans between opposite sides of the liner to divide it into a freezer compartment and a fresh food compartment. 
     A breaker strip  112  extends between a case front flange and outer front edges of liners. Breaker strip  112  is formed from a suitable resilient material, such as an extruded acrylo-butadiene-styrene based material (commonly referred to as ABS). 
     The insulation in the space between liners  108 ,  110  is covered by another strip of suitable resilient material, which also commonly is referred to as a mullion  114 . Mullion  114  also preferably is formed of an extruded ABS material. It will be understood that in a refrigerator with separate mullion dividing a unitary liner into a freezer and a fresh food compartment, a front face member of mullion corresponds to mullion  114 . Breaker strip  112  and mullion  114  form a front face, and extend completely around inner peripheral edges of case  106  and vertically between liners  108 ,  110 . Mullion  114 , insulation between compartments  102 ,  104 , and a spaced wall of liners  108 ,  110  separating compartments  102 ,  104  sometimes are collectively referred to herein as a center mullion wall  116 . 
     Shelves  118  and slide-out drawers  120  normally are provided in fresh food compartment  102  to support items being stored therein. A bottom drawer or pan  122  partly forms a quick chill and thaw system (not shown) and selectively controlled, together with other refrigerator features, by a microprocessor (not shown) according to user preference via manipulation of a control interface  124  mounted in an upper region of fresh food storage compartment  102  and coupled to the microprocessor. A shelf  126  and wire baskets  128  are also provided in freezer compartment  104 . In addition, an ice maker  130  may be provided in freezer compartment  104 . 
     A freezer door  132  and a fresh food door  134  close access openings to fresh food and freezer compartments  102 ,  104 , respectively. Each door  132 ,  134  is mounted by a top hinge  136  and a bottom hinge (not shown) to rotate about its outer vertical edge between an open position, as shown in FIG. 1, and a closed position (not shown) closing the associated storage compartment. Freezer door  132  includes a plurality of storage shelves  138  and a sealing gasket  140 , and fresh food door  134  also includes a plurality of storage shelves  142  and a sealing gasket  144 . 
     In accordance with known refrigerators, refrigerator  100  also includes a machinery compartment (not shown) that at least partially contains components for cooling air. The cooled air is used to refrigerate one or more refrigerator or freezer compartments via fans (not shown). The construction of the cooling system components is well known and therefore not described in detail herein. 
     Refrigerator  100  includes a plurality of temperature sensors  146 . In one embodiment, sensors  146  are thermistors. Alternatively, sensors  146  are thermocouples. Fresh food and freezer compartments  102 ,  104  each include a side wall  148 ,  150  respectively. Some sensors  146  are located on side walls  148  and  150  to avoid obstruction of compartments  102  and  104 . Additionally, some sensors  146  are located in mullion  114 . Although the purpose of sensors  146  are to sense the temperature of compartment  102  and  104 , sensors  146  sense the temperature of the location where each sensor  146  is located. Sometimes the measured temperature will be different from the true temperature in compartments  102  and  104 . Additionally, the measured temperature is also influenced by the temperatures and the temperature change on the other side of side walls  148  and  150  on or in which a particular sensor  146  is installed. For example, a sensor located in mullion  114  senses the temperature change on both fresh food compartment  102  and freezer compartment  104  because of heat transfer through mullion  114 . 
     Therefore, to improve the accuracy of the temperatures in compartments  102  and  104 , the temperature measurements from sensors  146  are corrected as described herein. The moving force of heat transfer through walls  148  and  150 , doors  132  and  134 , and mullion  114  is a temperature difference between the temperatures from both sides of the walls  148  and  150 , doors  132  and  134 , or mullion  114 . With good accuracy, the heat flux Q may be described by the equation Q=U*A*(T 1 −T 2 ), where U is a heat transfer coefficient that combines the influence of the heat transfer resistance from air to both sides of walls  148  and  150 , doors  132  and  134 , or mullion  114  with the conductance of walls  148  and  150 , doors  132  and  134 , or mullion  114  material. A is the surface area, and T 1  and T 2  are temperatures from a sensor mounted to an exterior surface and a sensor mounted to an interior surface of a wall, wherein the interior surface is interior to the compartment being measured and the exterior surface is exterior to the compartment but not necessary exterior to refrigerator  100 . For example, one sensor  146  is coupled to a surface of mullion  114  interior to fresh food compartment  102  and one sensor  146  is coupled to mullion  114  exterior to fresh food compartment  102  and interior to frozen food compartment  104 . Also, in one embodiment, the two different compartments are both above freezing but at different temperatures. 
     Also the surface area each particular sensor  146  is exposed to is also constant. So, with good accuracy the heat flux Q is proportional to dTw=T 1 −T 2  or Q=Cw*dTw (equation 1), where Cw is a constant that depends on the refrigerator and thermal sensor cavity geometry, and where dTw represents the temperature difference between a first sensor interior a compartment and a second sensor exterior the compartment. The temperature influence (dTs) on each sensor  146  from heat flux Q can be calculated as dTs=Q/(Us*As), where Us is the heat transfer coefficient from air to a particular sensor  146  and As is the sensor surface area exposed to the heat flux Q. During operation of the closed cooling system, sensors  146  do not move and therefore the areas As are constant. Although, airflow can influence the heat transfer coefficients Us, each sensor  146  is usually located in a cavity (not shown) with very small air movement within the cavity and changes in air movement within the cavity during a full cycle are not considerable. Therefore, Us also can be considered as a constant. Thus, dTs=Q/Cs (equation 2), where Cs is a constant. 
     Combination of equations (1) and (2) results in dTs=C*dTw (equation 3), where C is a constant combining two constants Cw and Cs. Constant C for each combination of sensors can be either calculated or found experimentally. The correction in the sensor temperature is done depending on the location of a particular sensor  146  and a difference between the temperatures from both sides of the wall. For any sensor(s) located in side walls  148  and  150 , or doors  132  and  134 , the sensor temperature correction is proportional to the difference between ambient temperature and the temperature of compartments  102  or  104 . 
     For sensor(s) located in mullion  114 , the sensor temperature correction is proportional to the difference between temperatures in adjacent compartments  102  and  104 . The temperatures in compartments  102  and  104  are known. Thus, for any sensor(s)  146  located in mullion  114 , there is no need for any additional temperature measurement. In other words, each compartment has an associated target temperature, say 1° for freezer compartment  104  and 35° for fresh food compartment  102 . The correction is then  34  times the constant coefficient. To correct the temperature from a sensor located in the walls or doors the ambient temperature is used. However, with an assumption that the ambient temperature in a kitchen is a constant the correction is calculated as dTs=Cc*Tc+Ca, where Cc and Ca are constants that can be determined by experiment. For example, fresh food compartment  102  has a target temperature of 38° and the ambient temperature is measured at 72°, then the correction factor is proportional to 72−38 which is 34. As used herein a target temperature is the temperature that the compartment is set to maintain. 
     FIG. 2 illustrates test data with the above described compensation of refrigerator  100 . The accuracy of the temperature was significantly improved over refrigerators which do not compensate the sensor readings. Accordingly, a cost effective refrigerator is provided that economically compensates for the difference between the true temperature in a compartment and the measured temperature in the compartment. Additionally, while described in the context of sensors mounted in mullions and side walls of refrigerators, it is contemplated that the benefits of the invention accrue to all cooling devices having temperature sensors. 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.

Technology Category: 2