Superheat control of air conditioning system incorporating fuel cooler

Reference Number: N 01-05

Inventors: Thompson, Michael B.; Torrence, Robert J.

Owner: NISTAC

USPTO Link: 4790145

Invention Summary

The present invention provides a heat exchanger disposed in the low pressure or return side of a continuously circulating positively pressurized engine fuel supply, such as that employed with engines having fuel injectors, for preventing vapor lock in the low pressure side of the fuel line returning fuel to the tank.

The present invention employs an electrically operated refrigerant expansion valve for controlling flow of refrigerant to the evaporator and the fuel line heat exchanger, and employs a microprocessor based controller to provide a pulse-width-modulated duty cycle signal to the refrigerant expansion valve for controlling flow of refrigerant in the system. A pressure transducer is disposed in the refrigerant line to measure the pressure of the refrigerant flowing therein as discharged from the evaporator and provides a signal to the microprocessor. The microprocessor then determines the saturation temperature of the refrigerant from a look-up table.

A temperature sensing thermistor is disposed in a refrigerant line between the fuel line heat exchanger and the compressor intake and provides a signal to the microprocessor of the actual temperature of the refrigerant discharging from the fuel line heat exchanger. The microprocessor then compares the saturation temperature with the actual temperature to determine the amount of superheat at the outlet of the fuel line heat exchanger and provides the pulse with modulated signal to the refrigerant expansion valve from a predetermined algorithm based upon the superheat at the outlet of the fuel line heat exchanger.

An optional feature of the invention permits the compressor for the air conditioning system to be initially energized upon command from the microprocessor based upon measurements of the temperature of the fuel in the fuel line.