Pressure adjuster valve and gas compressor using the same

A gas compressor comprising:

• a pair of side blocks;
• a cylindrical body disposed between the pair of side blocks;
• a rotor rotatably supported in the cylindrical body through bearings mounted on the pair of side blocks;
• a rotor shaft rotatably supported by the bearings;
• a plurality of vanes provided to be projectable and retractable from an outer circumferential surface of the rotor toward an inner wall of the cylindrical body;
• a compression chamber formed and partitioned by the cylindrical body, the pair of side blocks, the rotor and the vanes;
• a suction chamber formed at an upper flow side of the compression chamber;
• a back pressure chamber disposed in communication with bottom portions of the vanes;
• and
• a pressure adjuster valve comprised of a body having a communication passage for connecting the suction chamber in fluid communication with the back pressure chamber and a truncated conical-shaped valve seat portion disposed at one end of the communication passage, a valve element disposed within the communication passage to define a fine gap therebetween and movable within the communication passage to engage the valve seat portion of the body, and broadening means for partially broadening a width of the fine gap between the valve element and the communication passage;
• wherein when a pressure within one of the suction chamber and the back pressure chamber is lower than a pressure within the other of the suction chamber and the back pressure chamber, the valve element is pressed into engagement with the valve seat portion of the body by means of a pressure difference between the suction chamber and the back pressure chamber to thereby close the communication passage, and when the pressure within the suction chamber and the back pressure chamber are reversed, the valve element is moved away from the valve seat portion of the body by means of a pressure difference between the suction chamber and the back pressure chamber to thereby open the communication passage and equalize the pressures in the suction chamber and the back pressure chamber.