Fluid machine and refrigeration cycle apparatus

Abstract

A fluid machine ( 8 A) includes an expander ( 4 ) having an expander suction port ( 4 a ) and an expander discharge port ( 4 b ), a compressor ( 6 ) having a compressor suction port ( 6 a ) and a compressor discharge port ( 6 b ), and a shaft ( 81 ) coupling the expander ( 4 ) to the compressor ( 6 ). The expander suction port ( 4 a ) and the compressor suction port ( 4 a ) are opened and closed as the shaft ( 81 ) rotates. The expander suction port ( 4 a ) is opened during a period of time when the compressor suction port ( 6 a ) is closed, and the compressor suction port ( 6 a ) is opened and maintained out of communication with the compressor discharge port ( 6 b ) during a period of time when the expander suction port ( 4 a ) is closed.

1 . A fluid machine comprising:
 an expander that expands a working fluid drawn through an expander suction port and discharges the working fluid through an expander discharge port so as to recover power from the working fluid;   a compressor that increases a pressure of the working fluid drawn through a compressor suction port and discharges the working fluid through a compressor discharge port; and   a shaft that couples the expander to the compressor so that the compressor is driven by the power recovered by the expander,   wherein the expander suction port and the compressor suction port are opened and closed as the shaft rotates, and   the expander suction port is opened during a period of time when the compressor suction port is closed, and the compressor suction port is opened and maintained out of communication with the compressor discharge port during a period of time when the expander suction port is closed.   
     
     
         2 . The fluid machine according to  claim 1 ,
 wherein the shaft has a first eccentric portion for the expander and a second eccentric portion for the compressor,   the compressor includes a compressor piston into which the second eccentric portion is fitted, a compressor cylinder accommodating the compressor piston, and a compressor partition member partitioning a compressor working chamber formed between the compressor piston and the compressor cylinder into a suction side space and a discharge side space, and   within a period of time when the expander suction port is opened, the compressor piston passes a top dead center at which a sliding point of the compressor piston sliding on an inner circumferential surface of the compressor cylinder coincides with the compressor partition member.   
     
     
         3 . The fluid machine according to  claim 2 ,
 wherein the expander includes an expander piston into which the first eccentric portion is fitted, an expander cylinder accommodating the expander piston, and an expander partition member partitioning an expander working chamber formed between the expander piston and the expander cylinder into a suction side space and a discharge side space, and   0.25θo≦βv−βc≦0.75θo is satisfied where, when a rotation direction of the shaft is defined as positive, βc (−180°<βc≦180°) indicates a phase difference of an eccentric orientation of the second eccentric portion with respect to an eccentric orientation of the first eccentric portion, βv (−180°<βc≦180°) indicates a phase difference of a position of the compressor partition member with respect to a position of the expander partition member, and further θo indicates a rotation angle of the shaft during the period of time when the expander suction port is opened.   
     
     
         4 . The fluid machine according to  claim 2 ,
 wherein the compressor suction port is provided in the compressor cylinder and opens on the inner circumferential surface of the compressor cylinder, and   the expander suction port is closed after the compressor suction port is brought into communication with the suction side space of the compressor working chamber, and the expander suction port is opened before the suction side space of the compressor working chamber is brought into communication with the compressor discharge port.   
     
     
         5 . The fluid machine according to  claim 4 , wherein the compressor further includes a discharge valve for opening and closing the compressor discharge port owing to a pressure of the discharge side space of the compressor working chamber. 
     
     
         6 . The fluid machine according to  claim 2 ,
 wherein the compressor further includes an inner closing member for closing the compressor working chamber from a side of the expander and an outer closing member for closing the compressor working chamber from a side opposite to the expander,   the compressor suction port is provided in the inner closing member or the outer closing member so as to be exposed only to the suction side space of the compressor working chamber, and   the expander suction port is closed after the compressor suction port is brought into communication with the suction side space of the compressor working chamber, and the expander suction port is opened before the compressor suction port is closed.   
     
     
         7 . The fluid machine according to  claim 6 , wherein the compressor discharge port is provided in the inner closing member or the outer closing member so as to be exposed only to the discharge side space of the compressor working chamber. 
     
     
         8 . The fluid machine according to  claim 3 , wherein the expander further includes a drawing control mechanism for opening and closing the expander suction port as the shaft rotates. 
     
     
         9 . The fluid machine according to  claim 8 ,
 wherein the expander further includes an inner closing member for closing the expander working chamber from a side of the compressor and an outer closing member for closing the expander working chamber from a side opposite to the compressor,   the expander suction port is provided in the inner closing member or the outer closing member so as to penetrate through the inner closing member or the outer closing member, and   the drawing control mechanism is a rotor plate that is attached to the shaft so as to rotate while being in contact with a surface of the inner closing member or the outer closing member opposite to the expander working chamber and that has a large diameter portion for blocking the expander suction port and a small diameter portion for exposing the expander suction port.   
     
     
         10 . A refrigeration cycle apparatus using the fluid machine according to  claim 1 , comprising:
 a working fluid circuit through which a working fluid circulates, the working fluid circuit including a main compressor for compressing the working fluid, a radiator for radiating heat from the compressed working fluid, the expander for expanding the working fluid that has flowed out of the radiator, an evaporator for evaporating the expanded working fluid, and the compressor for increasing a pressure of the working fluid that has flowed out of the evaporator and supplying the working fluid to the main compressor; and   a bypass passage linking a portion between the main compressor and the radiator or a portion between the radiator and the expander to a portion between the evaporator and the compressor in the working fluid circuit.