Refrigerant circuit and compressor

A compressor incorporated in a refrigerant circuit, the compressor including a drive plate mounted on a drive shaft in a crank chamber and a piston located in a cylinder bore, wherein the drive plate is operably connected to the piston to convert rotation of the drive shaft to reciprocation of the piston, and wherein the drive plate is tiltable between a minimum inclination angle position and a maximum inclination angle position according to the difference between the pressure in the crank chamber and the pressure in the cylinder bore, wherein the piston moves by a stroke based on the inclination of the drive plate to change the displacement of the compressor, and wherein the piston compresses refrigerant gas supplied from an external low pressure passage of the refrigerant circuit to the cylinder bore through a suction chamber and discharges the compressed refrigerant gas from the cylinder bore to an external high pressure passage of the refrigerant circuit through a discharge chamber, the compressor comprising:

• a discharge muffler located between the discharge chamber and the external high pressure passage to suppress pulsation of refrigerant gas discharged from the discharge chamber;
• a check valve located between the discharge muffler and the external high pressure passage to selectively connect and disconnect the external high pressure passage with the discharge muffler, wherein the check valve is operated in accordance with the difference between the pressure in the discharge muffler and the pressure in the external high pressure passage to allow only discharge of refrigerant gas from the discharge muffler to the external high pressure passage;
• and
• a relief valve attached to the discharge muffler to release abnormally high pressure from the discharge muffler to the outside of the refrigerant circuit.

A refrigerant circuit that includes a compressor and an expansion valve, wherein a high pressure passage connects a discharge chamber in the compressor to the expansion valve to send high pressure refrigerant from the compressor to the expansion valve, and wherein a low pressure passage connects the expansion valve to a suction chamber in the compressor to send low pressure refrigerant from the expansion valve to the compressor, the refrigerant circuit comprising:

• a valve device located in the high pressure passage to selectively connect and disconnect the high pressure passage with the discharge chamber;
• a relief valve is located in the high pressure passage, wherein the relief valve is located upstream of the valve device;
• and
• a control valve disposed in the compressor for regulating the suction pressure in response to thermal information received by a controller.