Screw compressor

Abstract

The present invention provides a screw compressor in which an oil path is provided within the casing body such that the oil for sealing gaps in the compression chamber and lubricating the bearings is circulated to the vicinity of the low pressure side, allowing the compressor to have high adiabatic efficiency and high volumetric efficiency. The present invention also provides a screw compressor in which an oil path is provided in the screw bore outer circumferential portion of the casing body to prevent contact between the screw rotor and the screw bore portion of the casing body. The present invention also provides a screw compressor which includes a heat sink to increase the heat transfer area for exchanging heat between the oil and refrigerant gas or liquid refrigerant, thereby achieving increased resistance to returned liquid refrigerant.

1 . A screw compressor comprising: 
 a casing body;    a motor disposed within said casing body;    a screw rotor disposed such that the screw rotor rotates together with a rotor of said motor within said casing body; and    a compression chamber formed between said screw rotor and said casing body;    wherein an oil path is provided within said casing body to circulate an oil to a vicinity of the low pressure side of said compressor, said oil being introduced into said compression chamber to seal gaps in said compression chamber or lubricate a bearing.    
     
     
         2 . The screw compressor as claimed in  claim 1 , wherein said oil path is provided in a screw bore outer circumferential portion of said casing body.  
     
     
         3 . The screw compressor as claimed in  claim 1 , wherein a portion of said oil path protrudes externally of said casing body and has a solenoid valve attached thereto.  
     
     
         4 . The screw compressor as claimed in  claim 1 , wherein an oil temperature control device is provided on an inlet side of said oil path to control the temperature of said oil before said oil is introduced into said oil path.  
     
     
         5 . The screw compressor as claimed in  claim 4 , wherein: 
 said oil temperature control device is divided into two portions each attached to said oil path on a respective side of a screw bore outer circumferential portion of said casing body;    said oil is set at a high temperature before it is passed through said screw bore outer circumferential portion; and    said oil is set at a low temperature after it is passed through said screw bore outer circumferential portion.    
     
     
         6 . The screw compressor as claimed in  claim 4 , wherein: 
 a gap detector is provided to detect a gap between an inner circumferential portion of said casing body and said screw rotor; and    said temperature of said oil is controlled in accordance with detection results from said gap detector.    
     
     
         7 . The screw compressor as claimed in  claim 1 , wherein said oil path is extended to a vicinity of a power terminal portion and a terminal block of said motor disposed within said casing body.  
     
     
         8 . The screw compressor as claimed in  claim 1 , wherein: 
 said oil path is extended to a vicinity of a boundary wall of said casing body, said boundary wall constituting a boundary between a motor chamber and a low pressure chamber of said compressor; and    a heat sink is attached to said boundary wall such that said heat sink sits on both said motor chamber and said low pressure chamber of said compressor.    
     
     
         9 . A screw compressor comprising: 
 a casing body;    a motor disposed within said casing body;    a screw rotor disposed such that the screw rotor rotates together with a rotor of said motor within said casing body;    a screw shaft connected between said screw rotor and said motor rotor so as to align the axes of said screw rotor and said motor rotor;    a bearing for supporting said screw shaft; and    a compression chamber formed between said screw rotor and said casing body;    wherein an oil path is provided within said casing body to circulate an oil to a vicinity of the low pressure side of said compressor, said oil being introduced into said compression chamber to seal gaps in said compression chamber or lubricate said bearing.