Adaptive defrost control system for a refrigerator

Claim 1

A method of initiating a defrost operation in a refrigerator at the end of a defrost interval, the refrigerator including a refrigerated compartment, an evaporator for cooling the compartment and defrosting means for removing frost from the evaporator during a defrost operation including means responsive to the temperature of the evaporator for terminating the defrost operation, the method comprising the steps of: (a) developing a measure of the temperature of the evaporator during a defrost interval; (b) initiating a defrost operation; (c) measuring the duration of said defrost operation; (d) correcting the measured duration of said defrost operation by an amount determined by said measured evaporator temperature to derive a corrected defrost duration; and (e) initiating a subsequent defrost operation at the end of a subsequent defrost interval that is determined in accordance with the corrected defrost duration.

Claim 2

A method of initiating a defrost operation in a refrigerator at the end of a defrost interval, the refrigerator including a refrigerated compartment, an evaporator for cooling the compartment and defrosting means for removing frost from the evaporator during a defrost operation including means responsive to the temperature of the evaporator for terminating the defrost operation, the method comprising the steps of: (a) developing a measure of the temperature of the evaporator during a defrost interval; (b) initiating a defrost operation; (c) measuring the duration of said defrost operation; (d) correcting the measured duration of said defrost operation by an amount determined by said measured evaporator temperature to derive a corrected defrost duration; and (e) initiating a subsequent defrost operation at the end of a subsequent defrost interval that is determined in accordance with the corrected defrost duration.

Claim 9

A method of defrosting a refrigeration apparatus at the end of a variable defrost interval, said apparatus having means defining a refrigerated compartment, an access door for the compartment, an evaporator for cooling the compartment and defrosting means for effecting the removal of frost from the evaporator, the method comprising the steps of: (a) measuring the temperature within the refrigerated compartment during a defrost interval; (b) energizing the defrosting means to initiate a defrost operation; (c) measuring the length of time the defrosting means is energized during said defrost operation; (d) storing a count; (e) changing said stored count at a rate which is at least partly dependent upon said measured compartment temperature and said measured length of time the defrosting means is energized; and (f) initiating a subsequent defrost operation at the end of an adaptively variable interval the length of which is dependent upon the changing of the stored count to a predetermined number.

Claim 10

A method of defrosting a refrigeration apparatus at the end of a variable defrost interval, said apparatus having means defining a refrigerated compartment, an access door for the compartment, an evaporator for cooling the compartment and defrosting means for effecting the removal of frost from the evaporator, the method comprising the steps of: (a) measuring the temperature within the refrigerated compartment during a defrost interval; (b) energizing the defrosting means to initiate a defrost operation; (c) measuring the length of time the defrosting means is energized during said defrost operation; (d) storing a count; (e) changing said stored count at a rate which is at least partly dependent upon said measured compartment temperature and said measured length of time the defrosting means is energized; and (f) initiating a subsequent defrost operation at the end of an adaptively variable interval the length of which is dependent upon the changing of the stored count to a predetermined number.

Claim 11

A method of defrosting a refrigeration apparatus having means defining a compartment which is refrigerated to a below-freezing temperature, an access door for the compartment, an evaporator for cooling the compartment, electrically energizable defrosting means for removing frost from the evaporator, and means for terminating energization of the defrosting means when the evaporator reaches a predetermined temperature, the method comprising the steps of: (a) measuring the temperature within said below-freezing compartment; (b) initiating a defrost operation; (c) measuring the length of said defrost operation to develop a defrost operation duration; (d) changing the defrost operation duration by an amount which is dependent on said measured temperature to thereby obtain a corrected defrost duration which is proportional to the amount of frost removed from the evaporator during said defrost operation; (e) comparing said corrected defrost duration with a desired defrost duration to develop a comparison value; (f) developing a door weighting schedule that is a function of the comparison value; (g) accumulating door-open time when the compartment door is open at a rate determined by the weighting schedule; (h) initiating a subsequent defrost operation when a predetermined amount of door-open time has been accumulated; and (i) repeating steps (a) through (h).

Claim 12

A method of defrosting a refrigeration apparatus having means defining a compartment which is refrigerated to a below-freezing temperature, an access door for the compartment, an evaporator for cooling the compartment, electrically energizable defrosting means for removing frost from the evaporator, and means for terminating energization of the defrosting means when the evaporator reaches a predetermined temperature, the method comprising the steps of: (a) measuring the temperature within said below-freezing compartment; (b) initiating a defrost operation; (c) measuring the length of said defrost operation to develop a defrost operation duration; (d) changing the defrost operation duration by an amount which is dependent on said measured temperature to thereby obtain a corrected defrost duration which is proportional to the amount of frost removed from the evaporator during said defrost operation; (e) comparing said corrected defrost duration with a desired defrost duration to develop a comparison value; (f) developing a door weighting schedule that is a function of the comparison value; (g) accumulating door-open time when the compartment door is open at a rate determined by the weighting schedule; (h) initiating a subsequent defrost operation when a predetermined amount of door-open time has been accumulated; and (i) repeating steps (a) through (h).

Claim 13

A method of defrosting a refrigeration apparatus at the end of a variable interval, the refrigeration apparatus having defrosting means, a cabinet defining a refrigerated space, and a door for providing access to said space, the method comprising the steps of: (a) storing a signal having a first predetermined value; (b) sensing when the door is open; (c) changing the stored signal at a varying rate which decreases with time from an initial rate during a first door-open interval until a certain rate is reached; (d) changing said stored signal at a fixed rate less than the certain rate for door-open times in excess of the first door-open interval; and (e) initiating a defrost operation when the stored signal has been changed to a second predetermined value.

Claim 14

A method of defrosting a refrigeration apparatus at the end of a variable interval, the refrigeration apparatus having defrosting means, a cabinet defining a refrigerated space, and a door for providing access to said space, the method comprising the steps of: (a) storing a signal having a first predetermined value; (b) sensing when the door is open; (c) changing the stored signal at a varying rate which decreases with time from an initial rate during a first door-open interval until a certain rate is reached; (d) changing said stored signal at a fixed rate less than the certain rate for door-open times in excess of the first door-open interval; and (e) initiating a defrost operation when the stored signal has been changed to a second predetermined value.

Claim 15

A method of defrosting a refrigeration apparatus at the end of a variable interval, the refrigeration apparatus having means defining a below-freezing compartment and an above-freezing compartment, an access door for the below-freezing compartment, an access door for the above-freezing compartment, an evaporator for cooling the compartments and defrosting means for removing frost from the evaporator, the method comprising the steps of: (a) storing a count; (b) sensing when either or both of the compartment doors are open; (c) repeatedly changing the stored count by an amount that decreases with time during a first door-open interval of the above-freezing compartment door and repeatedly changing the stored count at a first fixed rate whenever said above-freezing compartment door remains open beyond the first door-open interval; (d) repeatedly changing said stored count at a second fixed rate throughout the period of time the below-freezing compartment door is open; and (e) initiating a defrost operation when the stored count reaches a predetermined value.

Claim 16

A method of defrosting a refrigeration apparatus at the end of a variable interval, the refrigeration apparatus having means defining a below-freezing compartment and an above-freezing compartment, an access door for the below-freezing compartment, an access door for the above-freezing compartment, an evaporator for cooling the compartments and defrosting means for removing frost from the evaporator, the method comprising the steps of: (a) storing a count; (b) sensing when either or both of the compartment doors are open; (c) repeatedly changing the stored count by an amount that decreases with time during a first door-open interval of the above-freezing compartment door and repeatedly changing the stored count at a first fixed rate whenever said above-freezing compartment door remains open beyond the first door-open interval; (d) repeatedly changing said stored count at a second fixed rate throughout the period of time the below-freezing compartment door is open; and (e) initiating a defrost operation when the stored count reaches a predetermined value.

Claim 19

A method of defrosting a refrigeration apparatus at the end of a variable interval, the refrigeration apparatus having means defining a below-freezing compartment and an above-freezing compartment, an access door for the below-freezing compartment, an access door for the above-freezing compartment, an evaporator for cooling the compartments and defrosting means for removing frost from the evaporator, the method comprising the steps of: (a) storing a count; (b) sensing when either or both of the compartment doors are open; (c) repeatedly changing the stored count by an amount that decreases with time during a first door-open interval of the above-freezing compartment door and repeatedly changing the stored count at a first fixed rate whenever said above-freezing compartment door remains open beyond the first door-open interval, including the steps of storing a weighting factor W and changing the stored count during the first door-open interval by an amount equal to 16(1/2).sup.t-1 W where t is the time in seconds that the above-freezing compartment door has been open; (d) repeatedly changing said stored count at a second fixed rate whenever the below-freezing compartment door is open; (e) initiating a defrost operation when the stored count reaches a predetermined value; (f) sensing the temperature of the below-freezing compartment prior to the initiation of the defrost operation; (g) measuring the duration of the defrost operation; (h) correcting the measured defrost duration by an amount dependent upon the sensed below-freezing compartment temperature; and (i) varying the weighting factor W in accordance with the corrected defrost duration.

Claim 20

A method of defrosting a refrigeration apparatus at the end of a variable interval, the refrigeration apparatus having means defining a below-freezing compartment and an above-freezing compartment, an access door for the below-freezing compartment, an access door for the above-freezing compartment, an evaporator for cooling the compartments and defrosting means for removing frost from the evaporator, the method comprising the steps of: (a) storing a count; (b) sensing when either or both of the compartment doors are open; (c) repeatedly changing the stored count by an amount that decreases with time during a first door-open interval of the above-freezing compartment door and repeatedly changing the stored count at a first fixed rate whenever said above-freezing compartment door remains open beyond the first door-open interval, including the steps of storing a weighting factor W and changing the stored count during the first door-open interval by an amount equal to 16(1/2).sup.t-1 W where t is the time in seconds that the above-freezing compartment door has been open; (d) repeatedly changing said stored count at a second fixed rate whenever the below-freezing compartment door is open; (e) initiating a defrost operation when the stored count reaches a predetermined value; (f) sensing the temperature of the below-freezing compartment prior to the initiation of the defrost operation; (g) measuring the duration of the defrost operation; (h) correcting the measured defrost duration by an amount dependent upon the sensed below-freezing compartment temperature; and (i) varying the weighting factor W in accordance with the corrected defrost duration.

Claim 24

A method of defrosting a refrigeration apparatus at the end of a variable interval, the refrigeration apparatus having means defining a below-freezing compartment and an above-freezing compartment, an access door for the below-freezing compartment, an access door for the above-freezing compartment, an evaporator for cooling the compartments and defrosting means for removing frost from the evaporator, the method comprising the steps of: (a) storing a count; (b) sensing when either or both of the compartment doors are open; (c) repeatedly changing the stored count by an amount that decreases with time during a first door-open interval of the above-freezing compartment door and repeatedly changing the stored count at a first fixed rate whenever said above-freezing compartment door remains open beyond the first door-open interval, including the steps of storing a weighting factor W and changing the stored count by the weighting factor W for each second the above-freezing compartment door is open beyond the first interval; (d) repeatedly changing said stored count at a second fixed rate whenever the below-freezing compartment door is open; (e) initiating a defrost operation when the stored count reaches a predetermined value; (f) sensing the temperature of the below-freezing compartment prior to the initiation of the defrost operation; (g) measuring the duration of the defrost operation; (h) correcting the measured defrost duration by an amount dependent upon the sensed below-freezing compartment temperature; and (i) varying the weighting factor W in accordance with the corrected defrost duration.

Claim 25

A method of defrosting a refrigeration apparatus at the end of a variable interval, the refrigeration apparatus having means defining a below-freezing compartment and an above-freezing compartment, an access door for the below-freezing compartment, an access door for the above-freezing compartment, an evaporator for cooling the compartments and defrosting means for removing frost from the evaporator, the method comprising the steps of: (a) storing a count; (b) sensing when either or both of the compartment doors are open; (c) repeatedly changing the stored count by an amount that decreases with time during a first door-open interval of the above-freezing compartment door and repeatedly changing the stored count at a first fixed rate whenever said above-freezing compartment door remains open beyond the first door-open interval, including the steps of storing a weighting factor W and changing the stored count by the weighting factor W for each second the above-freezing compartment door is open beyond the first interval; (d) repeatedly changing said stored count at a second fixed rate whenever the below-freezing compartment door is open; (e) initiating a defrost operation when the stored count reaches a predetermined value; (f) sensing the temperature of the below-freezing compartment prior to the initiation of the defrost operation; (g) measuring the duration of the defrost operation; (h) correcting the measured defrost duration by an amount dependent upon the sensed below-freezing compartment temperature; and (i) varying the weighting factor W in accordance with the corrected defrost duration.