Fluid machine

Abstract

A sub-compressor ( 23 ) is provided between a compressor ( 22 ) and a power-recovery device ( 24 ). A refrigerant after preliminarily being compressed by the sub-compressor ( 23 ) is allowed to flow into the compressor ( 22 ). Since the sub-compressor ( 23 ) and the power-recovery device ( 24 ) have approximately the same temperature, heat transfer hardly occur therebetween. Heat transfer occurs between the compressor ( 22 ) at high temperature and the sub-compressor ( 23 ) at low temperature. However, even if the heat from the compressor ( 22 ) heats the refrigerant in the sub-compressor ( 23 ), the refrigerant discharged from the sub-compressor ( 23 ) is delivered to the compressor ( 22 ), and thus the temperature of the sub-compressor ( 23 ) scarcely increases.

1 . A fluid machine comprising:
 a closed casing;   a rotation motor including a stator and a rotor, the rotation motor being disposed in the closed casing;   a compressor for compressing a refrigerant and discharging it into the closed casing, the compressor being disposed in the closed casing;   a power-recovery device for recovering power from the refrigerant by suctioning and discharging the refrigerant, the power-recovery device being disposed in the closed casing;   a shaft extending vertically, the shaft being shared by the rotation motor, the compressor and the power-recovery device; and   a sub-compressor for raising the pressure of the refrigerant and delivering the refrigerant to the compressor with the rotation of the shaft, the sub-compressor being disposed between the compressor and the power-recovery device.   
     
     
         2 . The fluid machine according to  claim 1 , wherein the compressor is located above the power-recovery device. 
     
     
         3 . The fluid machine according to  claim 2 , wherein an oil pool is formed in the bottom of the closed casing, the sub-compressor and the power-recovery device are disposed in the oil pool, and the compressor is located above the oil pool. 
     
     
         4 . The fluid machine according to  claim 3 , wherein the rotation motor is disposed between the compressor and the oil pool. 
     
     
         5 . The fluid machine according to  claim 3  further comprising an oil pump for supplying oil in the oil pool to the compressor, wherein the oil pump is located above the sub-compressor. 
     
     
         6 . The fluid machine according to  claim 5 , wherein a space filled with either of the refrigerant immediately before being suctioned into the sub-compressor, or the refrigerant immediately after being discharged from the sub-compressor is provided between the sub-compressor and the oil pump. 
     
     
         7 . The fluid machine according to  claim 1 , wherein the compressor is a scroll type. 
     
     
         8 . The fluid machine according to any  claim 1 , wherein the sub-compressor and the power-recovery device each are a rotary type. 
     
     
         9 . The fluid machine according to  claim 8 , wherein the power-recovery device is a fluid pressure motor. 
     
     
         10 . The fluid machine according to  claim 1 , wherein the refrigerant is carbon dioxide. 
     
     
         11 . The fluid machine according to  claim 1 , wherein the ratio of the suction volume of the sub-compressor with respect to the suction volume of the compressor is 1.2 or less.