A rotary fluid machine has an inner rotor and an outer shell held by a stationary support structure, arranged so that sealing points on the inside of the shell interact in a sealing arrangement with the outer surface of the rotor to define working chambers, such that in use the relative motion of the rotor to the shell causes fluid to be moved through ducts in the rotor and rotor shaft, between the working chambers and a point where the rotor shaft interacts with the support structure.

A system and method are presented for improved performance of gerotor compressors and expanders. Certain aspects of the disclosure reduce porting losses in a gerotor system. Other aspects of the disclosure provide for reduced deflection in lobes of an outer rotor of a gerotor system. Still other aspects of the disclosure provide for reduced leakage through tight gaps between components of a gerotor system.

A system and method are presented for improved performance of gerotor compressors and expanders. Certain aspects of the disclosure reduce porting losses in a gerotor system. Other aspects of the disclosure provide for reduced deflection in lobes of an outer rotor of a gerotor system. Still other aspects of the disclosure provide for reduced leakage through tight gaps between components of a gerotor system.

A system and method are presented for improved performance of gerotor compressors and expanders. Certain aspects of the disclosure reduce porting losses in a gerotor system. Other aspects of the disclosure provide for reduced deflection in lobes of an outer rotor of a gerotor system. Still other aspects of the disclosure provide for reduced leakage through tight gaps between components of a gerotor system.

A system and method are presented for improved performance of gerotor compressors and expanders. Certain aspects of the disclosure reduce porting losses in a gerotor system. Other aspects of the disclosure provide for reduced deflection in lobes of an outer rotor of a gerotor system. Still other aspects of the disclosure provide for reduced leakage through tight gaps between components of a gerotor system.

An arrangement (100) for specifying the pressure (64), produced by a pump (30) driven by an electric motor (31), includes a processor (116) which derives a target pressure value (64, 118) from an internal torque value (114) and a loss torque (108). The arrangement (100) further derives (112) the internal torque value (114) from a motor current value (110) and a motor constant k.sub.e.

An arrangement (100) for specifying the pressure (64), produced by a pump (30) driven by an electric motor (31), includes a processor (116) which derives a target pressure value (64, 118) from an internal torque value (114) and a loss torque (108). The arrangement (100) further derives (112) the internal torque value (114) from a motor current value (110) and a motor constant k.sub.e.

A positive displacement fluid pump is provided. The fluid pump includes a housing defining an internal cavity. A motor having a drive shaft that rotates about an axis is housed within the internal cavity of the housing. An internal plate is adjacent the motor and includes a central bore through which the drive shaft extends. The fluid pump further includes an external plate including an inlet in fluid communication with a suction port and an outlet in fluid communication with a delivery port. A pumping ring is sandwiched between the internal and external plates, and a pumping arrangement is located within the pumping ring and axially between the internal plate and the external plate. The pumping arrangement is rotatably coupled to the drive shaft such that rotation of the pumping arrangement by the drive shaft causes fluid to be pumped from the suction port to the delivery port.

There is provided an oil-free air compressor that prevents oil from entering a compressor body by preventing a reverse rotation of the compressor body when the compressor is in shutdown, while improving the rust prevention effect, and that has improved reliability. An oil-free air compressor 100 includes an oil-free compressor body 1 that compresses air, and that outputs the compressed air; a cooler 5 that is connected to the compressor body, and that cools the compressed high-temperature air; a dry air supply mechanism for supplying dry air to an output side of the compressor body; and a mechanism for preventing a reverse rotation of the compressor body during a shutdown of the compressor.

There is provided an oil-free air compressor that prevents oil from entering a compressor body by preventing a reverse rotation of the compressor body when the compressor is in shutdown, while improving the rust prevention effect, and that has improved reliability. An oil-free air compressor 100 includes an oil-free compressor body 1 that compresses air, and that outputs the compressed air; a cooler 5 that is connected to the compressor body, and that cools the compressed high-temperature air; a dry air supply mechanism for supplying dry air to an output side of the compressor body; and a mechanism for preventing a reverse rotation of the compressor body during a shutdown of the compressor.