Multi-Stage Rotary Compressor

Abstract

A multi-stage rotary compressor comprises: a casing having a sealed space therein; a driving unit installed in the casing, for generating a driving force; a first compression unit and a second compression unit for receiving the driving force from the driving unit and compressing a refrigerant; and a connection unit for connecting the first and second compression units and guiding the refrigerant discharged from the second compression unit to be sucked directly in the first compression unit and then re-compressed, by which it is possible to vary capacity, even using every plurality of compression units, and to obtain power saving effect suitable for a saving mode.

1 . A multi-stage rotary compressor, comprising:
 a casing having a sealed space therein;   a driving unit installed in the casing, for generating a driving force;   a first compression unit and a second compression unit for receiving the driving force from the driving unit and compressing a refrigerant; and   a connection unit for connecting the first and second compression units and guiding the refrigerant discharged from the second compression unit to be sucked directly in the first compression unit and then re-compressed.   
   
   
       2 . The compressor of  claim 1 , wherein the driving unit is formed as a constant-speed motor. 
   
   
       3 . The compressor of  claim 1 , wherein the first compression unit and the second compression unit have a different size of an inner space for sucking and compressing a compressed refrigerant, respectively. 
   
   
       4 . The compressor of  claim 3 , wherein a volume ratio between the volume of the inner space of a cylinder of the second compression unit and the volume of the inner space of the cylinder of the first compression unit is 1:0.5-0.8. 
   
   
       5 . The compressor of  claim 4 , wherein a volume ratio between the volume of the inner space of the cylinder of the second compression unit and the volume of the inner space of the cylinder of the first compression unit is 1:0.6-0.65. 
   
   
       6 . The compressor of  claim 1 , wherein the connection unit comprises:
 a suction pipe for guiding a refrigerant to a compression unit;   a chamber for covering a discharge valve of the second compression unit and then temporally storing the refrigerant discharged from the second compression unit; and   a first connection passage for guiding the refrigerant from the chamber to the first compression unit.   
   
   
       7 . The compressor of  claim 6 , wherein the chamber is installed at a lower portion of the compression unit for preventing a leakage of the refrigerant with maintaining a sealed state thereof. 
   
   
       8 . The compressor of  claim 6 , the first connection passage sequentially penetrates a bearing supporting the second compression unit in an axial direction and a side surface of the cylinder of the first compression unit in a direction of a radius thereof, and then is connected to the inner space of the first compression unit. 
   
   
       9 . The compressor of  claim 6 , wherein the first connection passage penetrates the casing thereby to be exposed to the external and then again penetrates the casing and the cylinder of the first compression unit in a direction of a radius thereof, thereafter being connected to the inner space of the first compression unit. 
   
   
       10 . The compressor of  claim 1 , wherein the connection unit comprises:
 a suction pipe for guiding a refrigerant to the second compression unit to compress the refrigerant;   a first chamber for covering a discharge valve of the second compression unit and temporally storing the refrigerant discharged from the second compression unit;   a second chamber for receiving the refrigerant from the first chamber and temporally storing the refrigerant;   a first connection passage for guiding the refrigerant from the first chamber to the second chamber; and   a second connection passage for guiding the refrigerant from the second chamber to the first compression unit.   
   
   
       11 . The compressor of  claim 10 , wherein the first chamber and the second chamber are positioned at a lower portion of the second compression unit and an upper portion of the first compression unit, respectively, thereby preventing a leakage of the refrigerant with maintaining a sealed state thereof. 
   
   
       12 . The compressor of  claim 11 , wherein the first connection passage penetrates a bearing supporting the compression unit and a cylinder of each compression unit in an axial direction. 
   
   
       13 . The compressor of  claim 11 , wherein the second connection passage covers an upper portion of the second compression unit, penetrates an upper bearing, and then connects the second chamber to the inner space of the first compression unit. 
   
   
       14 . The compressor of  claim 1 , wherein the connection unit selectively guides the refrigerant in order for the refrigerant discharged from the second compression unit to be sucked directly into the first compression unit thereafter to be compressed or to be compressed one time at each compression unit, and then discharged. 
   
   
       15 . The compressor of  claim 14 , wherein the connection unit comprises:
 a first suction pipe for guiding the refrigerant to the first compression unit;   a first control valve mounted on the first suction pipe, for controlling the sucked refrigerant;   a second suction pipe for guiding the refrigerant to the second compression unit;   a chamber for covering a second discharge valve which controls a discharged refrigerant of the second compression unit and temporally storing the refrigerant discharged from the second compression unit;   a second control valve for adjusting a flow direction of the refrigerant;   a first connection pipe for connecting the chamber to the second control valve;   a second connection pipe for connecting the second control valve to the first connection pipe to guide the refrigerant to the first compression unit; and   a third connection pipe for connecting the second control valve to the casing to guide the refrigerant to the inner space of the casing.   
   
   
       16 . The compressor of  claim 16 , wherein suction sides of the first and second suction pipes are connected to an accumulator separating gas-liquid of the refrigerant, respectively. 
   
   
       17 . The compressor of  claim 15 , wherein only one of the first and second suction pipes is connected to the accumulator. 
   
   
       18 . The compressor of  claim 15 , wherein the second control valve is a pilot valve.