Abstract:
A detection apparatus for detecting refrigerator door openings is coupled to at least one switch configured to be activated by a door opening. When the door is opened, the switch is activated and inputs a signal to the detection apparatus. The detection apparatus rectifies the signal; and phase-shifts the rectified signal so that it leads or lags the line voltage. The shifted output signal is fed to a processor that detects the opening of the door based upon the shifted signal. Signals output by a plurality of switches that generate a signal when activated mixed using an opto-coupler. Relative impedance of the lead and lag circuits may be adjusted to differentiate a phase shift of one shifted signal relative to another signal. The processor converts a value in degrees of phase shifting of the mixed signal to a time value, and based upon the time value, the processor determines which of the doors is open.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates generally to refrigerators and, more particularly, to methods and systems for detecting refrigerator door openings.  
           [0002]    Known refrigerator typically include a defrost system and one or more cooling system fans for moving air inside the refrigerator. The efficiency of the defrost system and the cooling system often are affected by and depend on the frequency and duration of opening of freezer and/or fresh food compartment doors. For example, a defrost may need to be executed as often when the doors are only infrequently opened, and operation of fans when the doors are open, thereby blowing cold air into the room is undesirable. Therefore, it is desirable for a refrigerator control system to detect the opening and closing of refrigerator and/or freezer compartment doors so that the refrigerator systems may be operated optimally and energy efficiently.  
           [0003]    One known method of detecting refrigerator door openings employs low-voltage magnetic (Hall effect) switches in positions redundant to door light switches. Magnetic switches, however, are expensive, and entail additional product assembly. Another known method of detecting refrigerator door openings employs detection circuits on each respective door interior light circuit, thus requiring a separate detection circuit for each door. Separate detection circuits also increase costs.  
         BRIEF SUMMARY OF THE INVENTION  
         [0004]    In an exemplary embodiment, a detection apparatus for detecting refrigerator door openings is coupled to at least one switch configured to be activated by a door opening. When the door is opened, the switch is activated and inputs a signal to the detection apparatus. The detection apparatus rectifies the signal; and phase-shifts the rectified signal so that it leads or lags a reference voltage, such as the line voltage. The shifted output signal is fed to a processor that detects the opening of the door based upon the shifted signal.  
           [0005]    More specifically, the phase shift is generated by lead and/or lag circuits to shift voltage of the switch activated signal to lead the line voltage by a lead value between zero degrees and 90 degrees or to lag the line voltage, by a lag value between zero degrees and −90 degrees.  
           [0006]    In one embodiment, the apparatus is configured to mix the phase-shifted signals output by a plurality of switches that generate a signal when activated. The signals are supplied to a processor and the mixed signal is isolated using an opto-coupler. Relative impedance of the lead and lag circuits may be adjusted to differentiate a phase shift of one shifted signal relative to another signal/ Because a frequency of the line voltage is known, in one embodiment, the processor converts a value in degrees of phase shifting of the mixed signal to a time value, and based upon the time value, the processor determines which of the doors is open using the time value.  
           [0007]    A detection apparatus is therefore provided that allows a single detection circuit to monitor opening of several doors, as well as to identify which of several doors is open. Thus, door openings may be detected in a cost effective manner and used to make energy efficient control decisions. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a perspective view of a refrigerator;  
         [0009]    [0009]FIG. 2 is a block diagram of a refrigerator controller in accordance with one embodiment of the present invention;  
         [0010]    [0010]FIG. 3 is a block diagram of the main control board shown in FIG. 2;  
         [0011]    [0011]FIG. 4 is a block diagram of the main control board shown in FIG. 2;  
         [0012]    [0012]FIG. 5 is a block diagram of an open door detection system;  
         [0013]    [0013]FIG. 6 is an illustration of waveforms produced by the system illustrated in FIG. 2;  
         [0014]    [0014]FIG. 7 is an illustration of lead and lag circuits;  
         [0015]    [0015]FIG. 8 is an illustration of a circuit for phase shift—quadrature detection; and  
         [0016]    [0016]FIG. 9 is an alternative embodiment of the circuit shown in FIG. 8. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]    [0017]FIG. 1 illustrates an exemplary side-by-side refrigerator  100  in which the invention may be practiced. It is contemplated, however, that the benefits of the invention accrue to other types of refrigerators and to other appliances where detection of door openings is desirable. Therefore, the description set forth herein is for illustrative purposes only and the invention is not limited to practice with any particular appliance, such as refrigerator  100 .  
         [0018]    Refrigerator  100  includes a fresh food storage compartment  102  and freezer storage compartment  104 . Freezer compartment  104  and fresh food compartment  102  are arranged side-by-side. A side-by-side refrigerator such as refrigerator  100  is commercially available from General Electric Company, Appliance Park, Louisville, Ky. 40225.  
         [0019]    Refrigerator  100  includes an outer case  106  and 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.  
         [0020]    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-syrene based material (commonly referred to as ABS).  
         [0021]    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 an 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, and a spaced wall of liners separating compartments, sometimes are collectively referred to herein as a center mullion wall  116 .  
         [0022]    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) selectively controlled, together with other refrigerator features, by a microprocessor (not shown in FIG. 1) 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. Shelves  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 .  
         [0023]    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 .  
         [0024]    In accordance with known refrigerators, refrigerator  100  also includes a machinery compartment (not shown) that at least partially contains components for executing a known vapor compression cycle for cooling air. The components include a compressor (not shown in FIG. 1), a condenser (not shown in FIG. 1), an expansion device (not shown in FIG. 1), and an evaporator (not shown in FIG. 1) connected in series and charged with a refrigerant. The evaporator is a type of heat exchanger which transfers heat from air passing over the evaporator to a refrigerant flowing through the evaporator, thereby causing the refrigerant to vaporize. The cooled air is used to refrigerate one or more refrigerator or freezer compartments via one or more fans (not shown in FIG. 1). Collectively, the vapor compression cycle components in a refrigeration circuit, associated fans, and associated compartments are referred to herein as a sealed system. The construction of the sealed system is well known and therefore not described in detail herein, and the sealed system is operable to force cold air through the refrigerator.  
         [0025]    [0025]FIG. 2 illustrates a controller  160  in accordance with one embodiment of the present invention. Controller  160  can be used, for example, in refrigerators, freezers and combinations thereof, such as, for example side-by-side refrigerator  100  (shown in FIG. 1).  
         [0026]    Controller  160  includes a diagnostic port  162  and a human machine interface (HMI) board  164  coupled to a main control board  166  by an asynchronous interprocessor communications bus  168 . An analog to digital converter (“A/D converter”)  170  is coupled to main control board  166 . AID converter  170  converts analog signals from a plurality of sensors including one or more fresh food compartment temperature sensors  172 , a quick chill/thaw feature pan (i.e., pan  122  shown in FIG. 1) temperature sensors  174 , freezer temperature sensors  176 , external temperature sensors (not shown in FIG. 2), and evaporator temperature sensors  178  into digital signals for processing by main control board  166 .  
         [0027]    In an alternative embodiment (not shown), A/D converter  170  digitizes other input functions (not shown), such as a power supply current and voltage, brownout detection, compressor cycle adjustment, analog time and delay inputs (both use based and sensor based) where the analog input is coupled to an auxiliary device (e.g., clock or finger pressure activated switch), analog pressure sensing of the compressor sealed system for diagnostics and power/energy optimization. Further input functions include external communication via IR detectors or sound detectors, HMI display dimming based on ambient light, adjustment of the refrigerator to react to food loading and changing the air flow/pressure accordingly to ensure food load cooling or heating as desired, and altitude adjustment to ensure even food load cooling and enhance pull-down rate of various altitudes by chancing fan speed and varying air flow.  
         [0028]    Digital input and relay outputs correspond to, but are not limited to, a condenser fan speed  180 , an evaporator fan speed  182 , a crusher solenoid  184 , an auger motor  186 , personality inputs  188 , a water dispenser valve  190 , encoders  192  for set points, a compressor control  194 , a defrost heater  196 , a door detector  198 , a mullion damper  200 , feature pan air handler dampers  202 ,  204 , and a quick chill/thaw feature pan heater  206 . Main control board  166  also is coupled to a pulse width modulator  208  for controlling the operating speed of a condenser fan  210 , a fresh food compartment fan  212 , an evaporator fan  214 , and a quick chill system feature pan fan  216 .  
         [0029]    [0029]FIGS. 3 and 4 are more detailed block diagrams of main control board  166 . As shown in FIGS. 3 and 4, main control board  166  includes a processor  230 . Processor  230  performs temperature adjustments/dispenser communication, AC device control, signal conditioning, microprocessor hardware watchdog, and EEPROM read/write functions. In addition, processor executes many control algorithms including sealed system control, evaporator fan control, defrost control, feature pan control, fresh food fan control, stepper motor damper control, water valve control, auger motor control, cube/crush solenoid control, timer control, and self-test operations.  
         [0030]    Processor  230  is coupled to a power supply  232  which receives an AC power signal from a line conditioning unit  234 . Line conditioning unit  234  filters a line voltage which is, for example, a 90-265 Volts AC, 50/60 Hz signal. Processor  230  also is coupled to an EEPROM  236  and a clock circuit  238 .  
         [0031]    A door switch input sensor  240  is coupled to fresh food and freezer door switches  242 , and senses a door switch state. A signal is supplied from door switch input sensor  240  to processor  230 , in digital form, indicative of the door switch state. Fresh food thermistors  244 , a freezer thermistor  246 , at least one evaporator thermistor  248 , a feature pan thermistor  250 , and an ambient thermistor  252  are coupled to processor  230  via a sensor signal conditioner  254 . Conditioner  254  receives a multiplex control signal from processor  230  and provides analog signals to processor  230  representative of the respective sensed temperatures. Processor  230  also is coupled to a dispenser board  256  and a temperature adjustment board  258  via a serial communications link  260 . Conditioner  254  also calibrates the above-described thermistors  244 ,  246 ,  248 ,  250 , and  252 .  
         [0032]    Processor  230  provides control outputs to a DC fan motor control  262 , a DC stepper motor control  264 , a DC motor control  266 , and a relay watchdog  268 . Watchdog  268  is coupled to an AC device controller  270  that provides power to AC loads, such as to water valve  190 , cube/crush solenoid  184 , a compressor  272 , auger motor  186 , a feature pan heater  206 , and defrost heater  196 . DC fan motor control  262  is coupled to evaporator fan  214 , condenser fan  210 , fresh food fan  212 , and feature pan fan  216 . DC stepper motor control  264  is coupled to mullion damper  200 , and DC motor control  266  is coupled to one or more sealed system dampers.  
         [0033]    Processor logic is used to make control decisions based at least in part on freezer door state and fresh food door state, i.e., frequency and duration of door opening and closing. Specifically, controller  160  activates one or more of loads in response to freezer door state and fresh food door state, including but not limited to operation of fresh food fan  212 , evaporator fan  214 , condenser fan  210 , a compressor relay, a defrost relay, and mullion damper stepper motor  264 .  
         [0034]    [0034]FIG. 5 illustrates, in block diagram form, an exemplary door detection apparatus  300  that determines door openings with phase shifting and quadrature phase detection of refrigerator interior light signals. Apparatus  300  employs door switches  242  (shown in FIG. 3) and more specifically a first door light switch  301  for freezer compartment door  132  (shown in FIG. 1) and a second light switch  302  for fresh food compartment door  134  (shown in FIG. 1). A half wave rectification and phase shift lag circuit  304  is coupled to first door light switch  301 , and a half wave rectification and phase shift lead circuit  306  in communication with second door switch  302 . An opto-coupler  305  is coupled to phase shift lag circuit  304  and phase shift lead circuit  306  for isolating and mixing respective signals, and a processor  307  is coupled to opto-coupler  305 . As described operationally below, detection apparatus  300  achieves electrically isolated, quadrature phase detection of opening of refrigerator doors  132 ,  134 .  
         [0035]    When either freezer compartment door  132  or fresh food compartment door  134  is opened, the respective first switch  301  or second switch  302  is activated to signal energization of interior lights for the respective refrigeration compartment. Signals from respective switches  301 ,  302  are rectified and phase shifted via circuits  304 ,  306 , and the phase-shifted signals are fed to opto-coupler  305 . A voltage signal input from first switch  301  is output as a signal that is nearly 90° behind of the line voltage whereas a signal input from second switch  302  is output as a voltage signal that is nearly 90° ahead of the line voltage. If switches  301 ,  302  are active at the same time, a signal is output that covers approximately 180° of the input line signal.  
         [0036]    [0036]FIG. 6 illustrates an exemplary waveform output of apparatus  300  in relation to the line or input signal. By comparing the output of signal of apparatus  300  with the reference line voltage, it may be determined whether one or both of refrigerator doors  132 ,  134  are open. Those in the art will recognize that these waveforms are produced by lead and lag circuits of equal impedance, and in this particular example, both the lead and lag circuits are tuned to about an 87° phase shift. It is recognized that the relative impedance of the lead and lag circuits can be adjusted to change the phase shift for one or both circuits to facilitate detection of which door has been opened.  
         [0037]    [0037]FIG. 7 illustrates exemplary phase lead and lag circuits  310 ,  312 . It is evident from these circuits that the phase lead may be adjusted from nearly 0 to 90°. Similarly, the lag may be adjusted from 0 to nearly −90 degrees. Since the line frequency is a fixed 50 or 60 Hertz, the degrees of lead or lag may be converted directly to a time value. Processor  230  (shown in FIG. 3) then uses the time values to determine which door is open.  
         [0038]    One exemplary circuit  320  for achieving the above described open door detection is illustrated schematically in FIG. 8. In this circuit, C 5  and R 9  provide a phase lead whereas C 4  and R 7  provide a phase lag. Q 1 , Q 2  and U 1  provide the mixing and level shifting functions. In alternative embodiments, a zero degree phase shift on one line and 90 degree phase shift (lead or lag) on the other is used. In a further embodiment, a single component for the mixing/level shifting function is used, as illustrated in FIG. 9.  
         [0039]    A detection apparatus is therefore provided that allows a single detection circuit to monitor opening of several doors, as well as to identify which of several doors is open. Thus, door openings may be detected in a cost effective manner and used to make energy efficient control decisions.  
         [0040]    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.