Patent ID: 7347673

Claim:
A fluid machine served as an expansion device and a compression device, the fluid machine introducing gas from a low pressure chamber into an operation chamber and compressing the gas in the operation chamber and discharging the gas into a high pressure chamber via a port when the fluid machine functions as the compression device, the fluid machine introducing the gas from the high pressure chamber into the operation chamber via the port and expanding the gas in the operation chamber and discharging the gas into the low pressure chamber when the fluid machine functions as the expansion device, comprising: a discharge valve serving as a differential pressure regulating valve for opening and closing the port in accordance with pressure difference between a pressure in the operation chamber and a pressure in the high pressure chamber, the discharge valve being movable between an operation position where the discharge valve functions as the differential pressure regulating valve and a non-operation position where the discharge valve fails to function as the differential pressure regulating valve and constantly opens the port; and an actuator operatively connected to the discharge valve for moving the discharge valve between the operation position and the non-operation position, the actuator positioning the discharge valve at the operation position when the fluid machine functions as the compression device, the actuator positioning the discharge valve at the non-operation position when the fluid machine functions as the expansion device.