Screw Compressor

Abstract

A screw compressor includes a screw rotor including: a rotor lobe part and a discharge-side shaft part; and a casing having a housing chamber that houses the rotor lobe part, a shaft hole through which the discharge-side shaft part passes, and a liquid feed path that introduces a liquid to the shaft hole. A second shaft section of the discharge-side shaft part disposed in the shaft hole and the shaft hole of the casing have a first opposed surface and a second opposed surface opposed to each other with a gap. The discharge-side shaft part has an annular groove on the first opposed surface, and the liquid feed path opens at a position opposed to the annular groove on the second opposed surface of the shaft hole. The second shaft section of the discharge-side shaft part and the shaft hole of the casing have, in an area remoter from the rotor lobe part than the annular groove, a tapered structure as a structure with a diameter smaller toward such a direction as to get further away from the rotor lobe part.

1 . A screw compressor comprising:
 a screw rotor including a rotor lobe part having a helical lobe and a shaft part provided at a discharge-side end of the rotor lobe part in an axial direction; and   a casing having a housing chamber that houses the rotor lobe part, a shaft hole through which the shaft part passes, and a liquid feed path that introduces to the shaft hole a liquid supplied from an external, the casing being configured to define working chambers together with the rotor lobe part, wherein   a predetermined portion of the shaft part disposed in the shaft hole and the shaft hole of the casing have a first opposed surface and a second opposed surface opposed to each other with a gap,   the shaft part has an annular groove on the first opposed surface,   the liquid feed path is configured so as to open on the second opposed surface of the shaft hole of the casing and at a position opposed to the annular groove, and   the predetermined portion of the shaft part and the shaft hole of the casing each have, in an area remoter from the rotor lobe part than a position of the annular groove, a structure with a diameter smaller toward such a direction as to get further away from the rotor lobe part.   
     
     
         2 . The screw compressor according to  claim 1 , wherein
 the structure is a stepped structure whose diameter smaller becomes toward such a direction as to get further away from the rotor lobe part.   
     
     
         3 . The screw compressor according to  claim 2 , wherein
 the stepped structure is configured to have only one step portion.   
     
     
         4 . The screw compressor according to  claim 2 , wherein
 the stepped structure is configured to have a plurality of step portions.   
     
     
         5 . The screw compressor according to  claim 1 , wherein
 the structure is a tapered structure whose diameter smaller becomes toward such a direction as to get further away from the rotor lobe part.   
     
     
         6 . The screw compressor according to  claim 5 , wherein
 the predetermined portion of the shaft part and the shaft hole of the casing are each configured to have whole of the area remoter from the rotor lobe part than the position of the annular groove as the tapered structure.   
     
     
         7 . The screw compressor according to  claim 5 , wherein
 the predetermined portion of the shaft part and the shaft hole of the casing are each configured to have only a part of the area remoter from the rotor lobe part than the position of the annular groove as the tapered structure.   
     
     
         8 . The screw compressor according to  claim 6 , wherein
 the predetermined portion of the shaft part and the shaft hole of the casing each have, also in an area closer to the rotor lobe part than the position of the annular groove, a tapered structure whose diameter becomes smaller toward such a direction as to get further away from the rotor lobe part.