Thermostatic expansion valve with electronic controller

Claim 1

A structural assembly for controlling operation of a refrigeration system comprising: (a) compressor means operable, upon energization, to circulate a flow of pressurized refrigerant; (b) condenser means receiving pressurized refrigerant from said compressor means and operable to liquify said refrigerant; (c) expansion means receiving liquified refrigerant from said condenser means and discharging said refrigerant at a substantially reduced pressure therefrom; (d) evaporator means receiving said reduced pressure liquified refrigerant from said expansion means and operable to absorb heat from the surrounding air and discharge vaporized refrigerant therefrom; (e) an means operative upon energization to direct a flow of cooling air to said condenser means; (f) clutch means operable upon actuation to effect energization of said compressor means; (g) thermistor means disposed to have said liquid refrigerant entering said expansion means flowing thereover; (h) first circuit means including limit resistor means operable to provide a flow of current through said thermistor means for effecting boiling of said refrigerant impinging on said thermistor means including means operative to compare the voltage on said thermistor means a reference, and including microcomputer means operative to determine the saturation temperature of said refrigerant and from a look up table of refrigerant determine the saturation pressure, said microcomputer means operative to provide an output control signal for performing a system function selected from the group consisting of (a) cycling said fan means; (b) control said clutch means when said saturation temperature exceeds predetermined limits; and, (i) second circuit means selectively operative to vary the current flow through said thermistor means for permitting or preventing self-heating of said thermistor means.

Claim 5

A method of controlling a refrigeration system for the type having compressor circulating refrigerant through a condenser then through an expansion means and then through an evaporator and then returning to the compressor comprising the steps of: (a) providing a thermistor in the refrigerant flow between the condenser and the expansion means; (b) flowing a first level of electrical current through said thermistor and heating said thermistor sufficiently to boil refrigerant impinging thereon and measuring the voltage across said thermistor; (c) comparing said measured voltage with a table of known properties of said thermistor for determining the saturation temperature of the flow; (d) providing a blower for directing a flow of air over said condenser and energizing said blower when saturation temperature exceeds a preselected upper limit and disabling said blower when said saturation temperature reaches a preselected lower limit; (e) flowing a second substantially lower level of current through said thermistor insufficient to boil refrigerant impinging thereon and measuring the voltage across said thermistor; and (f) comparing voltage measured with known properties of said thermistor and determining the refrigerant flow temperature disenabling the compressor when said temperature is below a preselected threshhold.

Claim 6

A method of controlling a refrigeration system for the type having compressor circulating refrigerant through a condenser then through an expansion means and then through an evaporator and then returning to the compressor comprising the steps of: (a) providing a thermistor in the refrigerant flow between the condenser and the expansion means; (b) flowing a first level of electrical current through said thermistor and heating said thermistor sufficiently to boil refrigerant impinging thereon and measuring the voltage across said thermistor; (c) comparing said measured voltage with a table of known properties of said thermistor for determining the saturation temperature of the flow; (d) providing a blower for directing a flow of air over said condenser and energizing said blower when saturation temperature exceeds a preselected upper limit and disabling said blower when said saturation temperature reaches a preselected lower limit; (e) flowing a second substantially lower level of current through said thermistor insufficient to boil refrigerant impinging thereon and measuring the voltage across said thermistor; and (f) comparing voltage measured with known properties of said thermistor and determining the refrigerant flow temperature disenabling the compressor when said temperature is below a preselected threshhold.