METHOD AND DEVICE FOR PREVENTING OVER COMPRESSION OF SCREW COMPRESSOR

摘要

PROBLEM TO BE SOLVED: To prevent over compression of a screw compressor and regulate capacity ratio Vi by a simple mechanism without requiring complicated mechanism such as a capacity control valve and a Vi variable valve.;SOLUTION: An over compression prevention valve 20 is disposed in a closed space Sc of a rotor chamber 12 right before communicating to a delivery space, and compressed gas is released to a delivery port 34 by opening the over compression prevention valve 20 if pressure in the closed space Sc exceeds an upper limit threshold. The over compression prevention valve 20 is provided with a valve element 24 and a coil spring 26 biasing the valve element 24 in a direction closing the bypass passage 40 at a recess part 22 provided at a bypass passage 40. A passage 42 communicating to a communication pipe 44 is provided at a deep end of the recess part 22. The communication pipe 44 can be changed over to a connection pipe 48 connected to a suction port 52 or a connection pipe 50 connected to a delivery port 34 by a three-way valve 46. The recess part 22 and the suction port 52 are connected and the over compression prevention valve 20 is opened if pressure in the closed space Sc exceeds the upper limit threshold.;COPYRIGHT: (C)2011,JPO&INPIT