Air-conditioning apparatus

1. An air-conditioning apparatus comprising:

a compressor into which an intermediate-pressure refrigerant is allowed to be injected in the course of compressing a refrigerant;

an outdoor heat exchanger;

an indoor heat exchanger;

a first path through which the refrigerant flows from the indoor heat exchanger to the outdoor heat exchanger;

an injection pipe including a first end being connected to the compressor and a second end being connected to the first path;

a flow passage switching device configured to switch connection of the outdoor heat exchanger;

a second path connecting the flow passage switching device to the outdoor heat exchanger;

an injection flow rate control device configured to control a flow rate of injection into the compressor;

an outdoor-side flow rate control device configured to generate an intermediate pressure for injection into the compressor and that is able to change a flow passage resistance in a continuous manner;

a bypass pipe bypassing the outdoor heat exchanger and the outdoor-side flow rate control device;

a bypass flow rate control device provided to the bypass pipe in parallel to the outdoor-side flow rate control device being configured to change a flow passage resistance in a continuous manner, and being configured to control an amount of heat exchange of the outdoor heat exchanger together with the outdoor-side flow rate control device; and

an indoor-side flow rate control device configured to adjust a flow rate of refrigerant to the indoor heat exchanger,

wherein the compressor, the outdoor heat exchanger, the flow passage switching device, the injection flow rate control device, the outdoor-side flow rate control device, and the bypass flow rate control device are provided within an outdoor unit,

wherein the indoor heat exchanger and the indoor-side flow rate control device are provided within an indoor unit,

wherein the indoor unit includes a plurality of indoor units, which are connected to the outdoor unit in parallel, and

wherein in accordance with an indoor load or an outside air temperature, one of control (a) and (b) is selectively performed:

(a) control of the amount of heat exchange of the outdoor heat exchanger by the outdoor-side flow rate control device and the bypass flow rate control device; and

(b) control of the intermediate pressure by the outdoor-side flow rate control device, the bypass flow rate control device, and the injection flow rate control device, and control of the flow rate of injection into the compressor in which the bypass flow rate control device is closed.

2. The air-conditioning apparatus of claim 1 , comprising

a relay unit interposed between the outdoor unit and the indoor units,

wherein the relay unit allows the indoor units to perform a cooling and heating mixed operation by switching a flow passage of the refrigerant so that cooling or heating is performed by each of the indoor units.

3. The air-conditioning apparatus of claim 2 , wherein

in an operation mode in which the outdoor heat exchanger operates as an evaporator,

a target value for the intermediate pressure differs between a case where none of the indoor units are performing cooling and a case where at least one indoor unit is performing cooling.

4. The air-conditioning apparatus of claim 1 ,

wherein in accordance with at least one piece of operation data out of the outside air temperature, an indoor temperature, the number of indoor units performing cooling and heating, and a pressure, a temperature, and a frequency of the compressor within the air-conditioning apparatus, switching is performed between the control of the amount of heat exchange of the outdoor heat exchanger and the control of the flow rate of injection into the compressor.

5. The air-conditioning apparatus of claim 1 ,

wherein a direction in which the refrigerant flows within the outdoor heat exchanger is fixed in one direction, regardless of whether the outdoor heat exchanger operates as a condenser or an evaporator.

6. The air-conditioning apparatus of claim 1 ,

wherein (a) the control of the amount of heat exchange of the outdoor heat exchanger is performed by continuously changing a flow rate of the refrigerant flowing into the outdoor heat exchanger.

7. The air-conditioning apparatus of claim 1 ,

wherein as a refrigerant for a heat source, difluoromethane or a refrigerant mixture of tetrafluoropropane and 15 mass percent or more of difluoromethane is used.

8. The air-conditioning apparatus of claim 1 ,

wherein the control of the flow rate of injection into the compressor is performed such that a discharge temperature of the refrigerant discharged from the compressor does not exceed 110 degrees Centigrade.

9. The air-conditioning apparatus of claim 1 ,

wherein the outdoor-side flow rate control device and the bypass flow rate control device cooperate with each other to, based on the outside air temperature, switch between (a) the control of the amount of heat exchange of the outdoor heat exchanger, and (b) the control of the intermediate pressure and the control of the flow rate of injection into the compressor.

10. The air-conditioning apparatus of claim 1 , further comprising:

a controller configured to control the injection flow rate control device, the outdoor-side flow rate control device, and the bypass flow rate control device, wherein

the controller is configured to selectively perform

(a) the control of the amount of heat exchange of the outdoor heat exchanger while closing the injection flow rate control device, and

(b) the control of the intermediate pressure and the control of the flow rate of injection into the compressor.

11. The air-conditioning apparatus of claim 10 ,

wherein the controller is configured to perform (b) the control of the intermediate pressure and the control of the flow rate of injection into the compressor while performing a heating operation in which the outdoor heat exchanger functions as a condenser and the indoor heat exchanger functions as an evaporator, and

wherein the controller is configured not to perform (b) the control of the intermediate pressure and the control of the flow rate of injection into the compressor while performing a cooling operation in which the outdoor heat exchanger functions as the evaporator and the indoor heat exchanger functions as the condenser.

12. The air-conditioning apparatus of claim 10 , wherein

the controller is configured to perform (b) the control of the intermediate pressure and the control of the flow rate of injection into the compressor after performing (a) the control of the amount of heat exchange of the outdoor heat exchanger.

13. The air-conditioning apparatus of claim 10 , wherein

the indoor heat exchanger includes a first indoor heat exchanger and a second indoor heat exchanger, and

the controller is configured to perform

a heating operation in which the first indoor heat exchanger and the second indoor heat exchanger each function as a condenser and the outdoor exchanger functions as an evaporator,

a cooling operation in which the first indoor heat exchanger and the second indoor heat exchanger each function as the evaporator and the outdoor exchanger functions as the condenser,

a heating main operation in which the first indoor heat exchanger functions as the condenser, the second indoor heat exchanger and the outdoor exchanger each function as the evaporator, and a first load of the first indoor heat exchanger is larger than a second load of the second indoor heat exchanger,

a cooling main operation in which the first indoor heat exchanger functions as the condenser, the second indoor heat exchanger and the outdoor exchanger each function as the evaporator, and a third load of the second indoor heat exchanger is larger than a fourth load of the first indoor heat exchanger.

14. The air-conditioning apparatus of claim 13 ,

wherein the controller is configured to perform (b) the control of the intermediate pressure and the control of the flow rate of injection into the compressor while performing one of the heating operation and the heating main operation, and

wherein the controller is configured not to perform (b) the control of the intermediate pressure and the control of the flow rate of injection into the compressor while performing one of the cooling operation and the cooling main operation.

15. The air-conditioning apparatus of claim 1 ,

wherein (a) the control of the amount of heat exchange of the outdoor heat exchanger is performed by changing the flow passage resistance of the bypass flow rate control device while the refrigerant flows through the outdoor heat exchanger.

16. The air-conditioning apparatus of claim 1 ,

wherein (a) the control of the amount of heat exchange of the outdoor heat exchanger includes

a first state in which the bypass flow rate control device is closed and the outdoor-side flow rate control device is opened such that the refrigerant flows through the outdoor heat exchanger and does not flow through the bypass flow rate control device, and

a second state in which the bypass flow rate control device and the outdoor-side flow rate control device are opened such that the refrigerant flows through the outdoor heat exchanger and the bypass flow rate control device.

17. The air-conditioning apparatus of claim 1 ,

wherein the first path includes a first portion being connected to the injection pipe and a second portion being connected to the bypass pipe,

the bypass pipe includes a first end being connected to the second path and a second end being connected to the second portion of the first path, and

the second portion provided to between the outdoor-side flow rate control device and the first portion of the first path.