Patent ID: 7347675

Claim:
A vane rotary expander including: a cylinder having a cylindrical inner wall; side plates closing both ends of the cylinder; a rotor disposed in the cylinder, an outer circumferential segment of the rotor defining a small clearance together with the inner wall of the cylinder; vanes inserted into vane grooves formed in the rotor at respective ends thereof so as to be freely slidable, the other ends of the vanes being in contact with the inner wall of the cylinder to form a plurality of operating chambers between the cylinder and the rotor; and a shaft integrally formed with the rotor, the shaft being rotatably supported about an axis, wherein a power for rotating the shaft is obtained by expanding a high-pressure operating fluid in the operating chamber, comprising: a first discharge port firstly communicating to the operating chamber involving in a discharging process and a second discharge port secondly communicating to the same operating chamber, both discharging ports being provided in the cylinder in a circumferential direction; a valve mechanism preventing the operating fluid from flowing back being provided to the first discharge port; and a discharge chamber temporarily storing the operating fluid flowing out from the first and second discharge ports, wherein: a pressure (Pc) applied to the operating chamber which has a maximum volume immediately before the operating chamber reaches the first discharge Port is set lower than a pressure (Pd) applied to the discharge chamber, and the expander is set so that the volume of the operating chamber is compressed again immediately after the operating chamber reaches the first discharge port to release the valve mechanism when the recompressed pressure exceeds the pressure applied to the discharge chamber; and a number of the vanes is n, the first discharge port is formed in the cylinder at a position of approximately {180×(1+1/n)} degrees from the small clearance in a direction where the shaft rotates, and the second discharge port is formed in the cylinder at any position in an area from an angle of approximately {180×(1+1/n)} degrees to an angle of 360 degrees from the small clearance in the direction where the shaft rotates.