Variable displacement compressor

A variable displacement compressor that draws, compresses, and discharges refrigerant gas, the compressor comprising:

• a housing, which includes a crank chamber, a cylinder bore, a suction chamber, and a discharge chamber;
• a drive shaft, which is supported in the housing to pass through the crank chamber;
• a cam plate, which is coupled to the drive shaft in the crank chamber, wherein the cam plate changes its inclination and integrally rotates with the drive shaft;
• a piston, which is coupled to the cam plate and reciprocates in the cylinder bore;
• a valve plate, which is located in the housing and separates the cylinder bore from the adjacent suction chamber, the valve plate including a suction port, a suction valve, a discharge port, and a discharge valve;
• an urging member, which is located between the housing and the drive shaft, wherein the urging member urges the drive shaft axially to separate the piston from the valve plate;
• a pressurizing passage, which connects the crank chamber to the discharge chamber;
• a bleed passage, which connects the crank chamber to the suction chamber;
• a displacement control valve, which is externally controlled and varies the pressure in the crank chamber by adjusting the size of an opening in at least one of the pressurizing passage and the bleed passage;
• wherein varying the inclination of the cam plate adjusts the displacement in accordance with the difference between the pressure in the crank chamber and the pressure in the cylinder bore;
• an external refrigerant circuit, which includes an evaporator and is connected to the suction chamber;
• a refrigerant duct, which connects the suction chamber to the evaporator;
• and
• a suction control valve, which is located in the refrigerant duct and is externally controlled to open and close the refrigerant duct, wherein the suction control valve closes the duct when the pressure in the crank chamber is above a predetermined level.