A system is provided for adjusting the volume ratio of a screw compressor. The system can use a port in a rotor cylinder to bypass vapor from the compression chamber to the discharge passage of the compressor. A valve can be used to open or close the port to obtain different volume ratios in the compressor.

A control valve includes: a first valve to control a flow rate of refrigerant flowing from a discharge chamber to a control chamber of a compressor; a second valve to control a flow rate of the refrigerant flowing from the control chamber to a suction chamber; a solenoid to generate a drive force in a first valve closing direction and a second valve opening direction; a biasing member to generate a biasing force in an first valve opening direction and a second valve closing direction; and a pressure sensing part to sense a pressure in the suction chamber or the control chamber, and generate a counterforce against the drive force. A state in which both of the first and second valves are open is present during an increase in the current supplied to the solenoid from zero to an upper limit current value, and an increase rate of an opening degree of the first valve is increased during a decrease in the current supplied to the solenoid, a predetermined lower limit current value being an inflection point of the increase.

An object of the present invention is to provide a rotary displacement compressor capable of determining whether a check valve has failed, and preventing the life of a compressor body from being reduced when a compression operation stops. In order to achieve the object, a rotary displacement compressor includes a compressor body that compresses a medium by reducing a volume of the medium using rotation; a discharge pipe through which a compressed medium, which is discharged through a discharge port of the compressor body, flows; a check valve that shuts off the compressed medium flowing backward to the compressor body; and a backflow control valve that allows a predetermined rate of the compressed medium to flow backward. The check valve and the backflow control valve are disposed in series via the discharge pipe.

A compressor system is provided that includes a contact cooled compressor and a coolant separator. The coolant separator is used to remove coolant fluid from a compressed flow stream produced by the contact cooled compressor during its operation. The coolant separator routes the removed coolant fluid back to the contact cooled compressor for further use. In some forms the coolant fluid is cooled prior to delivery back to the compressor. A stop valve can be provided in the coolant fluid return line to halt the flow of the fluid. A pressure sensitive member can be disposed to sense pressure of the coolant fluid that has been routed past the stop valve. Operation of the compressor can be changed as a result of the sensed pressure from the pressure sensitive member. Information from a temperature sensitive member can also be used to change operation of the compressor.

The disclosure relates to compressors for heat exchange systems, heat exchange systems having such compressors, and methods for controlling operation of compressors. The compressor includes a drive device for driving the compressor and having at least a first and second working conditions. An output power of the drive device under the second working condition is greater than an output power under the first working condition. The compressor has at least one upload/download flow path configured to be opened before the drive device is switched from the first working condition to the second working condition to reduce a suction flow of the compressor until current operating parameters of the compressor reach preset values, after which the switching is performed, and to increase the suction flow until the compressor is in a required working state, after the switching is completed.

A compressor system is provided that includes a contact cooled compressor and a coolant separator. The coolant separator is used to remove coolant fluid from a compressed flow stream produced by the contact cooled compressor during its operation. The coolant separator routes the removed coolant fluid back to the contact cooled compressor for further use. In some forms the coolant fluid is cooled prior to delivery back to the compressor. A stop valve can be provided in the coolant fluid return line to halt the flow of the fluid. A pressure sensitive member can be disposed to sense pressure of the coolant fluid that has been routed past the stop valve. Operation of the compressor can be changed as a result of the sensed pressure from the pressure sensitive member. Information from a temperature sensitive member can also be used to change operation of the compressor.

A control valve includes: a first valve to control a flow rate of refrigerant flowing from a discharge chamber to a control chamber of a compressor; a second valve to control a flow rate of the refrigerant flowing from the control chamber to a suction chamber; a solenoid to generate a drive force in a first valve closing direction and a second valve opening direction; a biasing member to generate a biasing force in an first valve opening direction and a second valve closing direction; and a pressure sensing part to sense a pressure in the suction chamber or the control chamber, and generate a counterforce against the drive force. A state in which both of the first and second valves are open is present during an increase in the current supplied to the solenoid from zero to an upper limit current value, and an increase rate of an opening degree of the first valve is increased during a decrease in the current supplied to the solenoid, a predetermined lower limit current value being an inflection point of the increase.

The present disclosure is directed to a screw compressor system having a rotor housing with a pair of screw rotors rotatably supported within a compression chamber. A suction side slide valve is in fluid communication with an inlet to the compression chamber. The suction side slide valve is movable between a closed position and a fully open position to define a variable suction side inlet volume for controlling capacity of the compressor.

A control valve includes: a first valve to control a flow rate of refrigerant flowing from a discharge chamber to a control chamber of a compressor; a second valve to control a flow rate of the refrigerant flowing from the control chamber to a suction chamber; a solenoid to generate a drive force in a first valve closing direction and a second valve opening direction; a biasing member to generate a biasing force in an first valve opening direction and a second valve closing direction; and a pressure sensing part to sense a pressure in the suction chamber or the control chamber, and generate a counterforce against the drive force. A state in which both of the first and second valves are open is present during an increase in the current supplied to the solenoid from zero to an upper limit current value, and an increase rate of an opening degree of the first valve is increased during a decrease in the current supplied to the solenoid, a predetermined lower limit current value being an inflection point of the increase.

A screw compressor includes a screw rotor, a rotor casing accommodating the screw rotor, and an internal-volume-ratio-adjusting valve capable of changing internal volume ratio. The internal-volume-ratio-adjusting valve includes a valve body movable along an axial direction of the screw rotor and defining a gas-discharge position, and a cylinder containing at least one pressurizing chamber with a cylinder rod and a piston. The cylinder rod is coupled to the valve body and disposed along the axial direction. The piston is fixed inside the pressurizing chamber to the cylinder rod and divides the pressurizing chamber into two pressurizing spaces along the axial direction. The screw compressor further includes a first communication passage connecting one of the two pressurizing spaces with the discharge gas passage, and a second communication passage connecting the other with a just-before-discharge tooth space immediately before a tooth space that communicates with the discharge port.