Patent ID: 7392659

Claim:
A method of controlling displacement in a variable displacement compressor of an automobile air conditioning system, the air conditioning system further including an evaporator and an air probe on the exit side of the evaporator, the method comprising: providing air conditioner control head parameter settings; providing an ambient temperature; providing a measured discharge pressure; providing an engine RPM; detecting an actual air temperature of air entering the evaporator and responsively producing an evaporator air-in temperature signal; detecting an actual humidity level of air entering the evaporator and responsively producing an evaporator air-in humidity signal; setting a target air temperature of the air probe; reading an actual air temperature of air exiting the evaporator at the air probe; calculating a suction pressure at an exit side of the evaporator, wherein calculating the suction pressure at an exit side of the evaporator is based on the target air temperature, a constant obtained from a lookup, table pertaining to the evaporator, and saturation pressure obtained from a refrigerant property table; calculating a load on the evaporator; calculating a refrigerant flow rate; and adjusting an operational state of the refrigerant compressor upon compressor startup, wherein adjusting an operational state of the refrigerant compressor means determining a swash plate angle to affect compressor displacement based in part on a result of calculating the suction pressure.