Refrigerator temperature and defrost control

In a refrigerator having cooling means for cooling a refrigerated compartment, defrost means coupled to the cooling means for defrosting a portion of the cooling means and sensing means for sensing the temperature of the portion of the cooling means, a control for operating the cooling means and the defrost means in accordance with the sensed temperature of said portion of the cooling means, comprising:

• means for determining when a particular frost load has accumulated on said portion of the cooling means;
• means coupled to the determining means for energizing the defrost means when the particular frost load has accumulated;
• and
• means coupled to the sensing means for de-energizing the defrost means when at least a part of the frost load has been removed and for energizing the cooling means when the temperature of said portion thereof reaches a predetermined temperature during the time the defrost means is deenergized including a power relay coupled to the cooling means and a control circuit for controlling the power relay, the control circuit including a temperature sensor for developing a temperature signal representing the temperature of the portion of the cooling means, a comparator coupled between the temperature sensor and the power relay for energizing the power relay when the magnitude of the temperature signal exceeds the magnitude of a set point signal and means for establishing the magnitude of the set point signal at a first magnitude during the time the cooling means is energized and for establishing the magnitude of the set point signal at a second magnitude greater than the first magnitude during the time the defrost means is energized.

In a refrigerator having cooling means for cooling a refrigerated compartment, defrost means coupled to the cooling means for defrosting a portion of the cooling means and sensing means for sensing the temperature of the portion of the cooling means, a control for operating the cooling means and the defrost means in accordance with the sensed temperature of said portion of the cooling means, comprising:

• means for determining when a particular frost load has accumulated on said portion of the cooling means;
• means coupled to the determining means for energizing the defrost means when the particular frost load has accumulated;
• and
• means coupled to the sensing means for de-energizing the defrost means when at least a part of the frost load has been removed and for energizing the cooling means when the temperature of said portion thereof reaches a predetermined temperature during the time the defrost means is deenergized including a power relay coupled to the cooling means and a control circuit for controlling the power relay, wherein the control circuit includes a first temperature sensor for developing a first temperature signal representing the temperature of the portion of the cooling means, a first comparator coupled between the first temperature sensor and the power relay for energizing the power relay when the magnitude of the temperature signal exceeds the magnitude of a first set point signal, a second temperature sensor for developing a second temperature signal representing the temperature of the refrigerated compartment and a second comparator coupled between the second temperature sensor and the power relay for energizing the power relay when the magnitude of the second temperature signal exceeds the magnitude of a second set point signal when the defrost means is de-energized.

In a refrigerator having a compartment, cooling means including an evaporator for cooling the compartment and defrost means for applying heat to the evaporator, a control for the cooling means and the defrost means, the control defining a cooling mode in which the cooling means is cyclically operated and a defrost mode in which the defrost means is operated, the control comprising:

• evaporator temperature sensing means responsive to the temperature of the evaporator to produce an output when a predetermined evaporator temperature is detected;
• compartment temperature sensing means for operating the cooling means during a cooling mode in response to the compartment temperature exceeding a predetermined compartment temperature;
• and
• switch means responsive to the evaporator temperature sensing means output for changing the control to a cooling mode when the control is in a defrost mode and for operating the cooling means when the control is in the cooling mode irrespective of the compartment temperature sensing means.

In a refrigerator having cooling means including an evaporator and a compressor for cooling a refrigerated compartment, the compressor having first and second power terminals, defrost means for heating the evaporator to remove frost therefrom, the defrost means having first and second power terminals, and a source of power coupled to first and second power conductors, an electrical control for controlling the application of power to the power terminals of each of the compressor and the defrost means, the control comprising:

• defrost initiation means for producing a defrost initiation signal upon a determination that the energization of the defrost means is desired;
• defrost termination means for producing a defrost termination signal upon a determination that the energization of the defrost means is not desired;
• temperature control means for producing a cooling signal upon a determination that energization of the compressor is desired;
• a first switch responsive to the defrost initiation means to assume a first condition electrically interconnecting the first power conductor to the first power terminal of the defrost means when the defrost initiation signal is produced;
• a second switch responsive to the defrost termination means and the temperature control means, the second switch assuming a first condition electrically interconnecting the second power conductor to the second power terminal of the defrost means in the absence of both the defrost termination signal and the cooling signal, so that energization of the defrost means will occur if also the first switch is in the first condition;
• the second switch assuming a second condition electrically interconnecting the second power conductor to the second power terminal of the compressor when the defrost termination signal is produced to de-energize the defrost means;
• the first switch being responsive to the defrost termination signal to assume a second condition electrically interconnecting the first power conductor to the first power terminal of the compressor;
• and
• the second switch assuming the second condition when the cooling signal is produced to energize the cooling means if also the first switch is in the second condition.