Fluid machine and refrigeration cycle apparatus

#The present invention relates to a fluid machine and a refrigeration cycle apparatus using the same to be used for a water heater, air-conditioner or the like.

#Recently, for the purpose of further improving the efficiency of a refrigeration cycle apparatus, there is proposed a power-recovery type refrigeration cycle apparatus using an expansion mechanism instead of an expansion valve in which the expansion mechanism recovers the pressure energy as power in the course of the expansion of a refrigerant (working fluid), thereby reducing the electric power required for driving a compression mechanism by the amount of the power recovered. Such a refrigeration cycle apparatus uses an expander compressor unit in which a motor, a compression mechanism and an expansion mechanism are coupled by a shaft.

#In the expander compressor unit, the compression mechanism and the expansion mechanism are coupled by the shaft, and therefore there may be a case where the displacement of the compression mechanism is insufficient, or the displacement of the expansion mechanism is insufficient, depending on the operational conditions. In order to ensure recovery power even under operational conditions where the displacement of the compression mechanism is insufficient so that the COP (Coefficient of Performance) of the refrigeration cycle apparatus can be kept high, there also is proposed a refrigeration cycle apparatus using a secondary compressor in addition to an expander compressor unit (see, for example, Patent literature 1). In this refrigeration cycle apparatus, the secondary compressor is operated so that the high pressure in a refrigeration cycle should be a specified target value.

#FIG. 1 is a schematic diagram indicating a refrigeration cycle apparatus using a fluid machine according to a first embodiment of the present invention.

#FIG. 2 is a vertical sectional view showing a first compressor according to the first embodiment.

#FIG. 3A is a horizontal sectional view taken along the line IIIA-IIIA, and

#Hereinafter, the embodiments of the present invention is described with reference to the drawings.

#FIG. 1 indicates a refrigeration cycle apparatus using a fluid machine 105 according to a first embodiment of the present invention. The refrigeration cycle apparatus includes a refrigerant circuit (working fluid circuit) 103 integrated with the fluid machine 105. The refrigerant circuit 103 includes a first compressor (expander compressor unit) 101, a second compressor 102, a heat radiator 4, an evaporator 6 and first to fourth pipes (refrigerant pipes) 3a to 3d for connecting these equipments. In this embodiment, the first compressor 101 and the second compressor 102 are coupled to each other by an oil-equalizing pipe 25, and the first compressor 101, the second compressor 102 and the oil-equalizing pipe 25 constitute the fluid machine 105.

#Specifically, the first discharge pipe 19 of the first compressor 101 and the second discharge pipe 20 of the second compressor 102 are connected to the heat radiator 4 via the first pipe 3a having two branch pipes and a main pipe leading therefrom. The heat radiator 4 is connected to a suction pipe 21 on the expansion side of the first compressor 101 via the second pipe 3b. A discharge pipe 22 on the expansion side of the first compressor 101 is connected to the evaporator 6 via the third pipe 3c. The evaporator 6 is connected to the first suction pipe 7 of the first compressor 101 and the second suction pipe 8 of the second compressor 102 via the fourth pipe 3d having a main pipe and two branch pipes leading therefrom.