Patent ID: 7533539

Claim:
A refrigerating machine comprising: an outdoor unit containing a compressor and an outdoor heat exchanger serving as a heat- source side heat exchanger; and a plurality of indoor units, wherein: each of the plurality of indoor units contains an indoor heat exchanger as a using side heat exchanger and is connected to the outdoor unit through an inter-unit pipe; one end of the outdoor heat exchanger is connected to both a refrigerant discharge pipe and a refrigerant suction pipe of the compressor, wherein the outdoor heat exchanger connection is selectively controlled by a first valve to provide a connection between the outdoor heat exchanger and to either the refrigerant discharge pipe or the refrigerant suction pipe of the compressor; the inter-unit pipe comprising: a high-pressure pipe, a low pressure pipe and a low-temperature high-pressure pipe, wherein: the high-pressure pipe is connected to the refrigerant discharge pipe, the low-pressure pipe is connected to the refrigerant suction pipe and the low-temperature high-pressure pipe is connected to the other end of the outdoor heat exchanger, one end of the indoor heat exchanger of each of the indoor units is connected to both the high-pressure pipe and the low-pressure pipe, wherein the one end of the indoor heat exchanger is selectively controlled by a second valve to provide a connection between the one end of the indoor heat exchanger and to either the high-pressure pipe or the low-pressure pipe; the other end of the indoor heat exchanger of each of the indoor units is connected to the low-temperature high-pressure pipe, the plural indoor units carry out either a cooling operation or a heating operation or carry out both the cooling operation and the heating operation in a mixing style at the same time; the compressor has an intermediate-pressure portion in which refrigerant having intermediate pressure higher than the pressure of the refrigerant at the suction side of the compressor and lower than the pressure of the refrigerant at the discharge side of the compressor is allowed to be introduced; and the refrigerating machine is further provided with a heat exchange circuit formed in the low-temperature high-pressure pipe between the heat-source side heat exchanger and the using side heat exchanger, wherein the heat exchange circuit: branches the refrigerant flowing from any one of the heat source-side heat exchanger and the using side heat exchanger, carries out heat exchange between a first branched refrigerant after the branching and any of the other branched refrigerant positioned after the branching and the refrigerant positioned before the branching so that the first branched refrigerant is set to a gas-phase refrigerant, and leads the gas-phase refrigerant thus achieved to any of the intermediate-pressure portion and the refrigerant suction pipe of the compressor.