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.

Control systems and methods for increasing efficiency of a compressor while the compressor capacity exceeds compressor load, by using a mechanical unloader such as a slide valve to reduce the internal volume ratio of the compressor and allow a more efficient speed to be maintained by a variable frequency drive (VFD) while reducing the compressor capacity based on the load. Control systems include the VFD, a controller for the VFD and the mechanical unloader, and temperature sensors. Compressor embodiments further include one or more compressors and mechanical unloaders operated by the control systems.

Control systems and methods for increasing efficiency of a compressor while the compressor capacity exceeds compressor load, by using a mechanical unloader such as a slide valve to reduce the internal volume ratio of the compressor and allow a more efficient speed to be maintained by a variable frequency drive (VFD) while reducing the compressor capacity based on the load. Control systems include the VFD, a controller for the VFD and the mechanical unloader, and temperature sensors. Compressor embodiments further include one or more compressors and mechanical unloaders operated by the control systems.

A screw compressor, method of operating, and refrigerant circuit are disclosed. The screw compressor includes a suction inlet that receives a working fluid to be compressed. A compression mechanism is fluidly connected to the suction inlet that compresses the working fluid. A discharge outlet is fluidly connected to the compression mechanism that outputs the working fluid following compression by the compression mechanism. A valve assembly is configured to vary a location at which the compression mechanism compresses the working fluid, the valve assembly being disposed to modify a suction location of the screw compressor.

A screw compressor comprising a compressor housing with a screw rotor chamber, two screw rotors, which are arranged in the screw rotor chamber, are mounted on the compressor housing so as to be rotatable about respective screw rotor axes, and mesh with one another, and also at least one control slide, which is arranged in a slide channel of the compressor housing, adjacently to both screw rotors by means of slide compression wall surfaces, is movable in a displacement direction parallel to the screw rotor axes, is rigidly connected to a piston rod that leads to a cylinder assembly for moving the at least one control slide, and is guided relative to the compressor housing by means of a guide insert that movably receives the piston rod in the displacement direction, wherein the piston rod is guided transversely to the displacement direction in the guide insert in elastically resilient fashion by means of a guide element.

Systems and methods are used to control operation of a rotary compressor of a refrigeration system to improve efficiency by varying the volume ratio and the speed of the compressor in response to current operating and load conditions. The volume of the axial and/or radial discharge ports of the compressor can be varied to provide a volume ratio corresponding to operating conditions. In addition, permanent magnet motors and/or control of rotor tip speed can be employed for further efficiency gains.

Systems and methods are used to control operation of a rotary compressor of a refrigeration system to improve efficiency by varying the volume ratio and the speed of the compressor in response to current operating and load conditions. The volume of the axial and/or radial discharge ports of the compressor can be varied to provide a volume ratio corresponding to operating conditions. In addition, permanent magnet motors and/or control of rotor tip speed can be employed for further efficiency gains.

A fluid machine includes a main body, two first screw rotors, two second screw rotors, a driving module, a first slide member and a second slide member. The two first screw rotors are meshingly engaged with each other. The two second screw rotors are meshingly engaged with each other. Two first screw rotors are arranged in the first chamber of the main body. Two second screw rotors are arranged in the second chamber of the main body. The driving module is arranged in the drive chamber of the main body. The first slide member can move relative to the two first screw rotors. The second slide member can move relative to the two second screw rotors. A fluid entering the main body exits after being compressed or expanded by the two first screw rotors and the two second screw rotors.

A variable capacity scroll compressor includes a fixed scroll. The fixed scroll of the compressor includes a bypass flow path configured to connect a suction unit to a compression unit, a cylinder space provided on the bypass flow path, and an on/off valve disposed to be movable back and forth in the cylinder space to open/close the bypass flow path according to a difference between a discharge pressure of the discharge unit and a suction pressure of the suction unit. Thus a capacity of the compressor may be reduced by connecting the suction unit to the compression unit under a low load condition in which a difference between a discharge pressure and a suction pressure is relatively less.

A variable capacity scroll compressor includes a fixed scroll. The fixed scroll of the compressor includes a bypass flow path configured to connect a suction unit to a compression unit, a cylinder space provided on the bypass flow path, and an on/off valve disposed to be movable back and forth in the cylinder space to open/close the bypass flow path according to a difference between a discharge pressure of the discharge unit and a suction pressure of the suction unit. Thus a capacity of the compressor may be reduced by connecting the suction unit to the compression unit under a low load condition in which a difference between a discharge pressure and a suction pressure is relatively less.