Screw compressor

Abstract

A screw compressor includes a first rotor provided with a helical groove, a second rotor meshing with the first rotor, and a rotor casing covering at least an outer periphery of the first rotor. The second rotor rotates together with the first rotor. The rotor casing defines a compression chamber in the helical groove together with the first rotor and the second rotor. A fluid is compressible in the compression chamber. At least one of the first rotor or the second rotor is provided with an oil supply passage connected to an oil supply port opened at a sliding surface of the rotor to supply a lubricant to the sliding surface.

1 . A screw compressor, comprising:
 a first rotor provided with a helical groove;   a second rotor meshing with the first rotor, the second rotor rotating together with the first rotor; and   a rotor casing covering at least an outer periphery of the first rotor, the rotor casing defining a compression chamber in the helical groove together with the first rotor and the second rotor,   a fluid being compressible in the compression chamber, and   at least one of the first rotor or the second rotor being is provided with an oil supply passage connected to an oil supply port opened at a sliding surface of the rotor to supply a lubricant to the sliding surface.   
     
     
         2 . The screw compressor of  claim 1 , further comprising:
 a switching mechanism configured to switch the oil supply passage between
 a supply state in which the lubricant is supplied to the sliding surface and 
 a non-supply state in which no lubricant is supplied to the sliding surface. 
   
     
     
         3 . The screw compressor of  claim 2 , wherein
 the switching mechanism is further configured
 to switch the oil supply passage to the supply state by causing an oil supply source to communicate with the oil supply passage when a rotational angle position of the rotor provided with the oil supply passage is in a predetermined angular range, and 
 to switch the oil supply passage to the non-supply state by blocking the oil supply source from the oil supply passage when the rotational angle position of the rotor is out of the predetermined angular range. 
   
     
     
         4 . The screw compressor of  claim 1 , wherein
 the first rotor is a screw rotor rotatably housed in a cylindrical wall constituting the rotor casing,   the second rotor is a gear-shaped gate rotor having a plurality of flat gates, the second gate rotor is arranged outside the cylindrical wall, and some of the gates enter a space inside the cylindrical wall via an opening formed in the cylindrical wall and mesh with the screw rotor so that the gate rotor rotates together with the screw rotor,   the oil supply passage is formed in at least one of the gates of the gate rotor, and   the oil supply port is a lateral oil supply port opened at a side surface of the at least one gate, and the side surface serves as the sliding surface which slides on the screw rotor.   
     
     
         5 . The screw compressor of  claim 4 , wherein
 the lateral oil supply port is opened at least at the side surface on a rear side in a direction of rotation of the at least one gate.   
     
     
         6 . The screw compressor of  claim 4 , wherein
 the oil supply passage is connected to a front oil supply port opened at a front surface of the at least one gate facing the compression chamber.   
     
     
         7 . The screw compressor of  claim 4 , wherein
 the lateral oil supply port includes at least one lateral oil supply port formed at a position closer to a base end of the at least one gate than a center of the at least one gate, in a radial direction of the gate rotor.   
     
     
         8 . The screw compressor of  claim 4 , further comprising:
 a support member supporting the gate rotor from a rear side opposite to the compression chamber; and   an oil sump formed between the support member and a coupling portion of the gate rotor coupling base ends of the plurality of gates, the oil sump being configured to have the lubricant supplied thereto, wherein   the oil supply passage extends in a radial direction of the gate rotor of the at least one gate, and has a base end connected to the oil sump.   
     
     
         9 . The screw compressor of  claim 1 , wherein
 the oil supply passage is formed in the first rotor, and   the oil supply port is an in-groove oil supply port opened at an inner surface of the helical groove serving as the sliding surface of the first rotor sliding on the second rotor.   
     
     
         10 . The screw compressor of  claim 1 , wherein
 the oil supply passage is formed in the first rotor, and   the oil supply port is an outer peripheral oil supply port opened at an outer peripheral surface of the first rotor serving as the sliding surface of the first rotor sliding on the rotor casing.   
     
     
         11 . The screw compressor of  claim 9 , wherein
 the first rotor has an oil sump formed at a position closer to a rotation axis of the first rotor than a bottom face of the helical groove, the oil sump being configured to have the lubricant supplied thereto, and   the oil supply passage extends from the oil sump toward an outer periphery of the first rotor.   
     
     
         12 . The screw compressor of  claim 10 , wherein
 the first rotor has an oil sump formed at a position closer to a rotation axis of the first rotor than a bottom face of the helical groove, the oil sump being configured to have the lubricant supplied thereto, and   the oil supply passage extends from the oil sump toward an outer periphery of the first rotor.   
     
     
         13 . The screw compressor of  claim 2 , wherein
 the first rotor is a screw rotor rotatably housed in a cylindrical wall constituting the rotor casing,   the second rotor is a gear-shaped gate rotor having a plurality of flat gates, the second gate rotor is arranged outside the cylindrical wall, and some of the gates enter a space inside the cylindrical wall via an opening formed in the cylindrical wall and mesh with the screw rotor so that the gate rotor rotates together with the screw rotor,   the oil supply passage is formed in at least one of the gates of the gate rotor, and   the oil supply port is a lateral oil supply port opened at a side surface of the at least one gate, and the side surface serves as the sliding surface which slides on the screw rotor.   
     
     
         14 . The screw compressor of  claim 3 , wherein
 the first rotor is a screw rotor rotatably housed in a cylindrical wall constituting the rotor casing,   the second rotor is a gear-shaped gate rotor having a plurality of flat gates, the second gate rotor is arranged outside the cylindrical wall, and some of the gates enter a space inside the cylindrical wall via an opening formed in the cylindrical wall and mesh with the screw rotor so that the gate rotor rotates together with the screw rotor,   the oil supply passage is formed in at least one of the gates of the gate rotor, and   the oil supply port is a lateral oil supply port opened at a side surface of the at least one gate, and the side surface serves as the sliding surface which slides on the screw rotor.