Screw compressor

Abstract

A screw compressor includes a screw rotor having a screw groove, a gate rotor having a gate that meshes with the screw groove, and a casing rotatably holding the screw rotor and covering the screw rotor from radially outside. The screw rotor, the gate rotor, and the casing form first and second compression chambers. The first compression chamber compresses a fluid at a first pressure to an intermediate pressure higher than the first pressure. The second compression chamber compresses the fluid at the intermediate pressure to a second pressure higher than the intermediate pressure. The casing has an intermediate chamber that communicates with the second compression chamber. The screw rotor and the casing are provided with a seal that seals the intermediate chamber and the first compression chamber. The first compression chamber is located above a center axis of the screw rotor.

1 . A screw compressor, comprising:
 a screw rotor having a screw groove;   a gate rotor having a gate that meshes with the screw groove; and   a casing rotatably holding the screw rotor and covering the screw rotor from radially outside,   the screw rotor, the gate rotor, and the casing forming
 a first compression chamber that compresses a fluid at a first pressure to an intermediate pressure higher than the first pressure, and 
 a second compression chamber that compresses the fluid at the intermediate pressure to a second pressure higher than the intermediate pressure, 
   the casing having an intermediate chamber that communicates with the second compression chamber,   the screw rotor and the casing being provided with a seal that seals the intermediate chamber and the first compression chamber, and   the first compression chamber being located above a center axis of the screw rotor.   
     
     
         2 . The screw compressor of  claim 1 , wherein
 the casing is provided with a communication passage that allows the intermediate chamber and the second compression chamber to communicate with each other, and   a lower end of the communication passage is located below an outermost diameter of a rotor including the screw rotor.   
     
     
         3 . The screw compressor of  claim 2 , wherein
 the intermediate chamber is a motor chamber that houses a motor rotor, and   the lower end of the communication passage is located below the outermost diameter of the rotor including the screw rotor and the motor rotor.   
     
     
         4 . The screw compressor of  claim 2 , wherein
 the communication passage has a hole formed in a wall of the casing.   
     
     
         5 . The screw compressor of  claim 2  wherein
 the communication passage includes one of
 an inclined portion that is inclined upward from the intermediate chamber toward the second compression chamber, and 
 a constricted portion that constricts a flow passage area of the communication passage.