Method and apparatus for controlling variable displacement compressor

摘要

A variable displacement compressor in a refrigeration circuit (38) using carbon dioxide refrigerant. The compressor changes the inclination of a swash plate (18) located in a control chamber (121) in accordance with the difference between the pressure in the control chamber (121) and the pressure in a suction chamber (131) thereby varying the compressor displacement. The compressor includes a control valve (25) that adjusts the difference between the pressure in the control chamber (121) and the pressure in the suction pressure (131). The control valve (25) controls the flow rate of refrigerant supplied from the discharge chamber (132) to the control chamber (121) thereby adjusting the pressure difference. A controller (33) inputs information from the outside of the refrigeration circuit (38). The outside information includes the outside temperature, the temperature of a passenger compartment and a target compartment temperature set by a temperature adjuster (36). The controller (33) sets a target value of the pressure of refrigerant discharged from the compressor in accordance with the outside information. The controller (33) then controls the current supplied to the control valve (25) such that the target discharge pressure is rapidly reached. The compressor reduces unnecessary operation thereby reducing the power consumption and the load.