JP5445494B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner in which a plurality of indoor units are connected to at least one outdoor unit, and more particularly to an air conditioner that can appropriately ensure the amount of refrigerant circulation in each indoor unit.

  2. Description of the Related Art Conventionally, a so-called air-conditioning-free air conditioning apparatus is known in which a plurality of indoor units are connected to at least one outdoor unit in parallel by refrigerant piping, and each indoor unit can perform a cooling operation and a heating operation simultaneously. In this air conditioner, for example, a plurality of indoor units are installed in different rooms, and a certain indoor unit performs a cooling operation, while another indoor unit can perform a heating operation.

  This type of air conditioner includes an outdoor unit including a compressor, an outdoor heat exchanger, a four-way valve, and an outdoor expansion valve, a plurality of indoor units including an indoor heat exchanger and an indoor expansion valve, and a plurality of A plurality of shunt units that are provided corresponding to the indoor unit and switch the direction of the refrigerant flowing in the indoor unit are connected to each other by a high-pressure gas pipe, a low-pressure gas pipe, and a liquid pipe.

  In this air conditioner, when the cooling / heating-free operation is performed, the outdoor heat exchanger is condensed when the operation load of the indoor unit that is performing the cooling operation is larger than the operation load of the indoor unit that is performing the heating operation. The four-way valve is switched so as to be a cooler (hereinafter, the operation in this state is referred to as cooling main operation). Conversely, when the operation of the indoor unit performing the heating operation becomes larger than the operation load of the indoor unit performing the cooling operation, the four-way valve is switched so that the outdoor heat exchanger becomes an evaporator (hereinafter, The operation in this state is referred to as heating-main operation). Further, the shunt unit is switched so that the indoor heat exchanger of the indoor unit performing the cooling operation is an evaporator and the indoor heat exchanger of the indoor unit performing the heating operation is a condenser.

  When performing cooling-dominated operation, for example, a part of the high-pressure refrigerant discharged from the compressor flows into the outdoor heat exchanger via the four-way valve, condenses by exchanging heat with the outside air, and is condensed by the outdoor expansion valve. The refrigerant is reduced in pressure to become an intermediate pressure refrigerant and flows into the indoor unit that performs the cooling operation through the liquid pipe. The intermediate-pressure refrigerant flowing into the indoor unit is decompressed by the indoor expansion valve to become a low-pressure refrigerant. The low-pressure refrigerant evaporates by exchanging heat with indoor air in the indoor heat exchanger, and is sucked into the compressor through the diversion unit and the low-pressure gas pipe.

  The remainder of the high-pressure refrigerant discharged from the compressor flows through the high-pressure gas pipe and into the indoor unit that performs the heating operation via the branch unit. The high-pressure refrigerant flowing into the indoor unit is condensed by exchanging heat with the indoor air in the indoor heat exchanger, and is reduced in pressure by the indoor expansion valve to become an intermediate-pressure refrigerant, and is cooled through the liquid pipe. It merges with the medium-pressure refrigerant flowing into the indoor unit.

  When performing the heating main operation, the high-pressure refrigerant discharged from the compressor flows through the high-pressure gas pipe and into the indoor unit that performs the heating operation through the branch unit. The high-pressure refrigerant that has flowed into the indoor unit is condensed by exchanging heat with indoor air in the indoor heat exchanger, and is reduced in pressure by the indoor expansion valve to become an intermediate-pressure refrigerant. The intermediate-pressure refrigerant depressurized by the indoor expansion valve flows from the indoor unit into the liquid pipe, and is divided into the outdoor heat exchanger side and the indoor unit side performing the cooling operation. The intermediate-pressure refrigerant flowing into the indoor unit is decompressed by the indoor expansion valve to become a low-pressure refrigerant. The low-pressure refrigerant evaporates by exchanging heat with indoor air in the indoor heat exchanger, and is sucked into the compressor through the diversion unit and the low-pressure gas pipe. On the other hand, the intermediate pressure refrigerant flowing into the outdoor heat exchanger exchanges heat with the outside air and evaporates to become a low pressure refrigerant, and is sucked into the compressor through the four-way valve and the low pressure gas pipe.

  As described above, in this air conditioner, air-conditioning-free operation is realized by switching refrigeration units and switching refrigeration units so that the indoor heat exchanger of each indoor unit individually becomes a condenser or an evaporator. ing.

  However, in such an air conditioner, the refrigerant pressure on the liquid pipe side and the high-pressure gas pipe side or the low-pressure gas pipe side of the indoor expansion valve provided in each indoor unit when performing an air-conditioning-free operation. In some cases, the difference may be reduced, and the amount of refrigerant circulating in the indoor unit that is performing the cooling operation or the indoor unit that is performing the heating operation may be reduced, and a reliable air conditioning operation may not be performed.

  For example, when the cooling main operation is performed (the outdoor heat exchanger is a condenser) and the pressure of the refrigerant flowing through the liquid pipe is high (the pressure difference with the refrigerant flowing through the high-pressure gas pipe is small) Since the indoor unit in operation has insufficient heating capacity, the opening of the indoor expansion valve is increased in order to increase the refrigerant flow rate in the indoor heat exchanger of the indoor unit. As the opening of the indoor expansion valve increases, the pressure difference between the liquid pipe side and the high-pressure gas pipe side of the indoor expansion valve becomes smaller and the refrigerant hardly flows through the indoor expansion valve. In such a state, there is a possibility that the refrigerant circulation amount may decrease in the indoor unit performing the heating operation.

  In order to solve the above-described problems, the opening of the outdoor expansion valve is adjusted to adjust the pressure of the refrigerant flowing through the liquid pipe, so that the liquid pipe side and the high-pressure gas pipe side or the low-pressure gas pipe of the indoor expansion valve are adjusted. By controlling so that the pressure difference from the side becomes equal to or greater than a predetermined value, the refrigerant circulation amount is secured in the indoor unit that is performing the cooling operation or the heating operation even when the cooling-free operation is performed. There has been proposed an air conditioner that prevents a cooling capacity or heating capacity of an indoor unit that is performing a cooling operation or a heating operation due to a decrease in temperature (for example, see Patent Document 1).

JP 2008-138954 A (pages 12 to 15, FIGS. 4 and 5)

  However, since the outdoor heat exchanger is used as a condenser in the above-described Patent Document 1 when the cooling-main operation is performed, the pressure of the refrigerant flowing through the liquid pipe can be adjusted by adjusting the opening of the outdoor expansion valve. However, when heating-based operation is performed, an outdoor heat exchanger is used as an evaporator, and the outdoor expansion valve adjusts the opening according to the degree of superheat of the refrigerant. The pressure of the flowing refrigerant cannot be adjusted. Therefore, when heating-dominated operation is performed (when the outdoor heat exchanger is an evaporator), it becomes impossible to control the pressure difference between the liquid pipe side of the indoor expansion valve and the high-pressure gas pipe side or the low-pressure gas pipe side. There is a possibility that the amount of refrigerant circulating in the indoor unit performing the operation or the heating operation is reduced and the cooling capacity or the heating capacity is insufficient.

  The present invention solves the problems described above, and even when an outdoor heat exchanger provided in an outdoor unit is used as an evaporator, the liquid pipe side and the high-pressure gas pipe side or low-pressure gas of the indoor expansion valve are used. By adjusting the pressure of the refrigerant flowing through the liquid pipe so that the pressure difference from the pipe side is equal to or greater than a predetermined value, it is possible to suppress a decrease in the refrigerant circulation amount in the indoor unit that is performing the cooling operation or the heating operation. Features.

  In order to solve the above-described problems, in the air conditioner of the present invention, a plurality of indoor units including at least one outdoor unit including a compressor, an outdoor heat exchanger, and an outdoor expansion valve, and an indoor heat exchanger are provided. A high-pressure gas pipe, a low-pressure gas pipe, and a liquid pipe for connecting the outdoor unit, the plurality of indoor units, and the plurality of diversion units to each other. I have. Furthermore, a bypass pipe provided with a flow rate adjusting valve is provided between the high pressure gas pipe and the liquid pipe and between the liquid pipe and the low pressure gas pipe. And, when the air conditioning apparatus is performing air-conditioning-free operation, the pressure difference before and after the indoor expansion valve provided in the indoor unit performing the cooling operation or heating operation becomes smaller than a predetermined value Is configured to adjust the pressure of the refrigerant flowing through the liquid pipe by opening and closing the flow rate adjusting valve of the bypass pipe as appropriate so that the high pressure gas pipe and the liquid pipe or the low pressure gas pipe and the liquid pipe communicate with each other.

  According to the air conditioner of the present invention configured as described above, the pressure of the refrigerant flowing through the liquid pipe is adjusted by opening and closing the flow rate adjustment valve of each bypass pipe. As a result, even when an outdoor heat exchanger is used as an evaporator, the liquid pipe side and the high-pressure gas pipe side or the low-pressure gas pipe side of the indoor expansion valve provided in the indoor unit for which high operating capacity is required. Since the pressure difference can be adjusted, it is possible to prevent a decrease in the refrigerant circulation amount between the indoor units, and to suppress a shortage of operating capacity due to the decrease in the refrigerant circulation amount in each indoor unit.

It is a refrigerant circuit diagram explaining the flow of the refrigerant | coolant in the case where all the indoor units perform air_conditionaing | cooling operation in the air conditioning apparatus which is an Example of this invention. It is a refrigerant circuit figure explaining the flow of a refrigerant in case all the indoor units perform heating operation in the air harmony device which is an example of the present invention. It is a refrigerant circuit figure explaining the flow of the refrigerant in the case of performing the cooling main operation in the air harmony device which is an example of the present invention. It is a refrigerant circuit figure explaining the flow of the refrigerant in the case of performing heating main operation in the air harmony device which is an example of the present invention. It is a refrigerant circuit figure explaining the raise / lower of a liquid pipe refrigerant pressure in case the outdoor heat exchanger is a condenser in the air conditioning apparatus which is an Example of this invention. It is a refrigerant circuit figure explaining rise / fall of a liquid pipe refrigerant pressure in case an outdoor heat exchanger is an evaporator in an air harmony device which is an example of the present invention. It is a flowchart explaining control of a liquid pipe refrigerant pressure in the air conditioning apparatus which is an Example of this invention.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. As an embodiment, an air conditioner will be described as an example in which five indoor units are connected in parallel to one outdoor unit and can be operated free of air conditioning. The present invention is not limited to the following embodiments, and can be variously modified without departing from the gist of the present invention.

  FIG. 1 to FIG. 4 are refrigerant circuit diagrams for explaining the refrigerant flow in each operation state of the air-conditioning apparatus 1 in this embodiment. FIG. 1 is a diagram when all the indoor units are performing a cooling operation. 2 shows a case where all the indoor units are performing the heating operation, FIG. 3 shows a case where the cooling main operation is performed, and FIG. 4 shows a case where the heating main operation is performed. In the following description, when a configuration common to the refrigerant circuit is described regardless of the operation state, FIG. 1 will be described as a representative diagram.

  As shown in FIG. 1, the air conditioner 1 in the present embodiment includes one outdoor unit 2, five indoor units 8 a to 8 e, five branch units 6 a to 6 e, and a high-pressure gas pipe 30. The low-pressure gas pipe 31, the liquid pipe 32, and the control unit 100 are provided. The outdoor unit 2, the indoor units 8a to 8e, and the diversion units 6a to 6e are connected to each other by the high pressure gas pipe 30, the low pressure gas pipe 31, and the liquid pipe 32, thereby forming a refrigerant circuit.

  The outdoor unit 2 mainly includes a compressor 21, a four-way valve 22, an outdoor heat exchanger 23, an accumulator 24, an oil separator 25, an outdoor fan 26, a first bypass pipe 33, and a second bypass pipe 34. And an outdoor expansion valve 40, a first expansion valve 41 that is a first flow rate adjusting means, a second expansion valve 42 that is a second flow rate control means, and closing valves 43 to 45.

  The compressor 21 is a variable capacity compressor that can vary its operating capacity by being driven by a motor (not shown) whose rotational speed is controlled by an inverter. As shown in FIG. 1, the discharge side of the compressor 21 is connected to a closing valve 43 via an oil separator 25, and a pipe branched from between the oil separator 25 and the closing valve 43 is connected to the four-way valve 22. Has been. The suction side of the compressor 21 is connected to the closing valve 45 via the accumulator 24.

  The four-way valve 22 is a valve for switching the direction in which the refrigerant flows, and includes four ports a to d as shown in FIG. In this four-way valve 22, the port a is connected to the discharge side of the compressor 21 as described above, the port b is connected to the outdoor heat exchanger 23, and the port c is connected to piping connecting the accumulator 24 and the closing valve 45. ing. The port d is sealed. The other of the outdoor heat exchangers 23 is connected to the closing valve 44 via the outdoor expansion valve 40.

  In the air conditioner 1, as shown in FIGS. 1 and 3, when the indoor units 8a to 8e are all performing the cooling operation, the cooling main operation (the load required for the indoor unit performing the cooling operation is the heating operation). When the air conditioner 1 is operated in a state that is larger than the load required by the indoor unit that performs the operation, the port a and the port b of the four-way valve 22 are simultaneously communicated with each other. It switches so that it may connect, and the outdoor heat exchanger 23 is functioned as a condenser.

Further, as shown in FIGS. 2 and 4, when all the indoor units 8 a to 8 e perform the heating operation, the heating main operation (the load required by the indoor unit performing the heating operation is performing the cooling operation). When the air conditioner 1 is operated in a state larger than the load required by the indoor unit), the port a and the port d of the four-way valve 22 are communicated and at the same time the port b and the port c are switched. Thus, the outdoor heat exchanger 23 functions as an evaporator.
1 to 4, the ports that communicate with the four-way valve 22 are indicated by solid lines, and the ports that do not communicate are indicated by broken lines.

  As described above, the accumulator 24 is interposed between the suction side of the compressor 21 and the closing valve 45. The accumulator 24 separates the refrigerant that has flowed into gas refrigerant and liquid refrigerant, and causes the compressor 21 to suck only the gas refrigerant.

  The oil separator 25 is connected to the discharge side of the compressor 21, separates the refrigeration oil mixed in the gas refrigerant discharged from the compressor 21 from the gas refrigerant, and returns it to the compressor 21. The outdoor fan 26 is rotated by a fan motor (not shown) to take outside air into the outdoor unit 2, and after the heat exchange between the refrigerant and the outside air in the outdoor heat exchanger 23, the outdoor air after heat exchange to the outside of the outdoor unit 2. Is discharged.

  The outdoor expansion valve 40 is interposed between the outdoor heat exchanger 23 and the closing valve 44. When the outdoor heat exchanger 23 functions as a condenser, the outdoor expansion valve 40 is fully opened or detected by the discharge pressure of the compressor 21 detected by the high pressure sensor 50 and the intermediate pressure sensor 57. It is adjusted according to the difference from the hydraulic pressure. Further, when the outdoor heat exchanger 23 functions as an evaporator, the degree of opening of the outdoor heat exchanger 23 is the degree of superheat of the refrigerant in the outdoor heat exchanger 23 (the low-pressure saturation temperature calculated from the suction pressure detected by the low-pressure sensor 51 and the outdoor heat exchange). And the refrigerant outlet temperature detected by a heat exchange outlet temperature sensor (not shown) provided on the four-way valve 22 side of the vessel 23).

  The first bypass pipe 33 has one end connected to a pipe connecting the discharge side (oil separator 25) of the compressor 21 and the closing valve 43, and the other end connected to a pipe connecting the outdoor expansion valve 40 and the closing valve 44. And connected to bypass both pipes. A first expansion valve 41 is interposed in the first bypass pipe 33, and the amount of refrigerant flowing through the first bypass pipe 33 is adjusted by adjusting the opening degree of the first expansion valve 41, or the first The first bypass pipe 33 can be shut off by fully closing the expansion valve 41.

  The second bypass pipe 34 has one end connected to a pipe connecting the outdoor expansion valve 40 and the closing valve 44, and the other end connected to a pipe connecting the suction side (accumulator 24) of the compressor 21 and the closing valve 45. Connected to bypass both pipes. A second expansion valve 42 is interposed in the second bypass pipe 34, and the amount of refrigerant flowing through the second bypass pipe 34 is adjusted by adjusting the opening of the second expansion valve 42, or the second The second bypass pipe 34 can be shut off by fully closing the expansion valve 42.

  In addition to the configuration described above, the outdoor unit 2 is provided with various sensors. As shown in FIG. 1, the outdoor unit 2 is a high-pressure refrigerant pressure detection unit that detects the pressure of a high-pressure gas refrigerant flowing through the pipe connected to the discharge side of the compressor 21 and the closing valve 43. The high-pressure sensor 50 and a discharge temperature sensor 52 that detects the temperature of the high-pressure gas refrigerant discharged from the compressor 21 are provided in a pipe near the discharge side of the compressor 21. In addition, a low-pressure sensor 51 serving as a low-pressure refrigerant pressure detecting means for detecting the pressure of a low-pressure gas refrigerant flowing in the pipe is connected to a pipe connecting the suction side of the compressor 21 and the closing valve 45, and a suction of the compressor 21. A pipe near the side is provided with a suction temperature sensor 53 that detects the temperature of the low-pressure gas refrigerant sucked into the compressor 21.

  Further, the outdoor heat exchanger 23 is provided with a heat exchange temperature sensor 55 that detects the temperature of the refrigerant flowing in the outdoor heat exchanger 23. The pipe connecting the outdoor expansion valve 40 and the closing valve 44 includes an intermediate pressure sensor 57 that is a liquid pipe refrigerant pressure detecting means for detecting the pressure of the refrigerant flowing through the liquid pipe 32 and the temperature of the refrigerant flowing through the liquid pipe 32. And a refrigerant temperature sensor 54 for detecting. Further, an outdoor air temperature sensor 56 for detecting the temperature of the outside air flowing into the outdoor unit 2, that is, the outside air temperature, is provided near the outside air inlet (not shown) of the outdoor unit 2.

  The five indoor units 8a to 8e mainly include indoor heat exchangers 81a to 81e, indoor expansion valves 82a to 82e, and indoor fans 83a to 83e. In addition, since the structure of all the indoor units 8a-8e is the same, in the following description, only the structure of the indoor unit 8a is demonstrated, and description is abbreviate | omitted about the other indoor units 8b-8e.

  One of the indoor heat exchangers 81a is connected to the liquid pipe 32 via the indoor expansion valve 82a, and the other is connected to a branching unit 6a described later by refrigerant piping. The indoor heat exchanger 81a functions as an evaporator when the indoor unit 8a performs a cooling operation, and functions as a condenser when the indoor unit 8a performs a heating operation.

As described above, the indoor expansion valve 82a is interposed on the liquid pipe 32 side of the indoor heat exchanger 81a. When the indoor heat exchanger 81a functions as an evaporator, the indoor expansion valve 82a is adjusted according to the required cooling capacity, and when the indoor heat exchanger 81a functions as a condenser, The opening is adjusted according to the required heating capacity.
The indoor fan 83a is rotated by a fan motor (not shown), thereby taking in indoor air into the indoor unit 8a, exchanging heat between the refrigerant and the indoor air in the indoor heat exchanger 81a, and supplying the indoor air to the room.

  In addition to the configuration described above, the indoor unit 8a is provided with various sensors. As shown in FIG. 1, a liquid side temperature sensor 84a for detecting the temperature of the refrigerant is provided in a pipe on the indoor expansion valve 82a side of the indoor heat exchanger 81a, and a pipe on the diversion unit 6a side of the indoor heat exchanger 81a. Are respectively provided with gas side temperature sensors 85a for detecting the temperature of the refrigerant. Further, a room temperature sensor 86a for detecting the temperature of the indoor air flowing into the indoor unit 8a, that is, the room temperature is provided in the vicinity of the indoor air suction port (not shown) of the indoor unit 8a.

  The air conditioner 1 includes five branch units 6a to 6e corresponding to the five indoor units 8a to 8e described above. The diversion units 6a to 6e mainly include first electromagnetic valves 61a to 61e, second electromagnetic valves 62a to 62e, first diversion pipes 63a to 63e, and second diversion pipes 64a to 64e. In addition, since all the structures of the flow dividing units 6a-6e are the same, in the following description, only the structure of the flow dividing unit 6a is demonstrated and description is abbreviate | omitted about the other flow dividing units 6b-6e.

  As shown in FIG. 1, one end of the first branch pipe 63 a is connected to the high pressure gas pipe 30, and one end of the second branch pipe 64 a is connected to the low pressure gas pipe 31. The other end of the first branch pipe 63a, the other end of the second branch pipe 64a, and the liquid pipe 32 are connected to the indoor heat exchanger 81a. The first solenoid valve 61a is provided in the first branch pipe 63a, and the second solenoid valve 62a is provided in the second branch pipe 64a. The first solenoid valve 61a and the second solenoid valve 62a are opened and closed, respectively. As a result, the indoor heat exchanger 81a of the indoor unit 8a corresponding to the flow dividing unit 6a is connected to the discharge side (high pressure gas pipe 30 side) or the suction side (low pressure gas pipe 31 side) of the compressor 21. The flow path of the refrigerant in the circuit can be switched.

  The connection state of the outdoor unit 2, the indoor units 8a to 8e and the diversion units 6a to 6e described above with the high pressure gas pipe 30, the low pressure gas pipe 31, and the liquid pipe 32 is as follows. One end of the high-pressure gas pipe 30 is connected to the closing valve 43 of the outdoor unit 2, and the other end of the high-pressure gas pipe 30 is branched and connected to the first branch pipes 63a to 63e of the branch units 6a to 6e. One end of the low pressure gas pipe 31 is connected to the closing valve 45 of the outdoor unit 2, and the other end of the low pressure gas pipe 31 is branched and connected to the second branch pipes 64a to 64e of the branch units 6a to 6e.

One end of the liquid pipe 32 is connected to the closing valve 44 of the outdoor unit 2, and the other end of the liquid pipe 32 is branched and connected to the indoor expansion valves 82a to 82e side of the indoor units 8a to 8e. In addition, the indoor heat exchangers 81a to 81e side of the corresponding indoor units 8a to 8e and the diversion units 6a to 6e are respectively connected by refrigerant pipes.
With the connection described above, the refrigerant circuit of the air conditioner 1 is configured, and the refrigeration cycle is established by flowing the refrigerant through the refrigerant circuit.

  Further, the outdoor unit 2 of the air conditioner 1 is provided with a control unit 100. The control unit 100 mainly includes a CPU 110, a storage unit 120, and a communication unit 130. The CPU 100 captures detection signals from the sensors of the outdoor unit 2 and captures control signals output from the indoor units 8 a to 8 e via the communication unit 130. The CPU 110 controls the compressor 21, the four-way valve 22, the outdoor expansion valve 40, the first expansion valve 41, and the second expansion valve 42 based on the acquired detection signal and control signal.

  The storage unit 120 includes an EEPROM and a RAM, and stores detection values corresponding to control programs for the outdoor unit 2 and detection signals from each sensor. The communication unit 130 is an interface that performs communication with the indoor units 8a to 8e.

In addition, although illustration is abbreviate | omitted, each indoor unit 8a-8e is also equipped with the control part. The control units of the indoor units 8a to 8e take in detection signals from the sensors of the indoor units 8a to 8e and take in control signals from a remote controller of the air conditioner 1 (not shown). The control units of the indoor units 8a to 8e control the indoor units 8a to 8e based on the captured detection signals and control signals. Moreover, according to the operation mode (cooling operation / heating operation) of the indoor units 8a to 8e, the first electromagnetic valve 61a and the second electromagnetic valve 62a of the corresponding flow dividing units 6a to 6e are opened and closed, respectively.
The control unit 100 described above and the control units provided in the indoor units 8a to 8e constitute a control unit of the air conditioner apparatus 1.

  Next, the operation | movement operation | movement of the air conditioning apparatus 1 in a present Example is demonstrated. In the air conditioner 1, the setting of the four-way valve 22 provided in the outdoor unit 2 (connection state of the ports a to d) and the first electromagnetic valves 61a to 61e and the second electromagnetic valve 62a provided to the flow dividing units 6a to 6e. Various driving operations are possible depending on the open / close state of .about.62e. In the following description, a typical driving operation is taken as an example from these driving operations.

  In the following description, the outdoor heat exchanger 23 and the indoor heat exchangers 81a to 81e are hatched when they are condensers, and are illustrated with white when they are evaporators. The open / closed states of the first electromagnetic valves 61a to 61e and the second electromagnetic valves 62a to 62e in the flow dividing units 6a to 6e are illustrated in black when they are closed, and are illustrated in white when they are open. In the following description, it is assumed that the first expansion valve 41 and the second expansion valve 42 are both fully closed and the first bypass pipe 33 and the second bypass pipe 34 are blocked.

  First, the case where all the indoor units 8a to 8e perform the cooling operation will be described with reference to FIG. As shown in FIG. 1, in this operation, the control unit 100 sets the port a and the port b of the four-way valve 22 to communicate with each other and the port c and the port d to communicate with each other. Moreover, the control part of each indoor unit 8a-8e closes the 1st electromagnetic valve 61a-61e of corresponding branch unit 6a-6e, and opens 2nd electromagnetic valve 62a-62e. Thereby, the outdoor heat exchanger 23 becomes a condenser, and all the indoor heat exchangers 81a to 81e of the indoor units 8a to 8e become evaporators.

  The high-pressure refrigerant discharged from the compressor 21 flows into the rear outdoor heat exchanger 23 after passing through the four-way valve 22. The high-pressure refrigerant flowing into the outdoor heat exchanger 23 is condensed by exchanging heat with the outside air. The refrigerant condensed in the outdoor heat exchanger 23 passes through the outdoor expansion valve 40 that is fully opened by the control unit 100, flows through the liquid pipe 32, and flows into each of the indoor units 8a to 8e.

  The intermediate-pressure refrigerant that has flowed into the indoor units 8a to 8e is decompressed by the indoor expansion valves 82a to 82e, becomes low-pressure refrigerant, and flows into the indoor heat exchangers 81a to 81e. The low-pressure refrigerant that has flowed into the indoor heat exchangers 81a to 81e exchanges heat with room air and evaporates, thereby cooling the room where the indoor units 8a to 8e are installed. Here, the indoor expansion valves 82a to 82e are the evaporators based on the refrigerant temperature detected by the liquid side temperature sensors 84a to 84e and the refrigerant temperature detected by the gas side temperature sensors 85a to 85e by the control unit of the indoor units 8a to 8e. The degree of refrigerant superheat at the outlets of the indoor heat exchangers 81a to 81e is obtained, and the opening degree is determined accordingly.

  Specifically, the refrigerant flow rate is small with respect to the size of the cooling capacity required by the indoor units 8a to 8e, and the superheat degree of the refrigerant at the outlets of the indoor heat exchangers 81a to 81e increases accordingly. Then, the control part of indoor unit 8a-8e enlarges the opening degree of indoor expansion valve 82a-82e, and increases the flow volume of a refrigerant | coolant. In addition, in the case where the refrigerant flow rate is large with respect to the size of the cooling capacity required by the indoor units 8a to 8e, and accordingly the degree of superheat of the refrigerant at the outlets of the indoor heat exchangers 81a to 81e is small, The control units of the machines 8a to 8e reduce the flow rates of the refrigerant by reducing the openings of the indoor expansion valves 82a to 82e.

  The low-pressure refrigerant that has flowed out of the indoor heat exchangers 81a to 81e flows into the diversion units 6a to 6e, and flows through the second diversion pipes 64a to 64e provided with the open second electromagnetic valves 62a to 62e to low pressure. It flows into the gas pipe 31. Then, the low-pressure refrigerant that flows into the low-pressure gas pipe 31 from each of the branch units 6a to 6e and merges in the low-pressure gas pipe 31 flows into the outdoor unit 2, passes through the accumulator 24, is sucked into the compressor 21, and is compressed again. Is done.

  Next, the case where all the indoor units 8a to 8e perform the heating operation will be described with reference to FIG. As shown in FIG. 2, in this operation, the control unit 100 sets the port a and the port d of the four-way valve 22 to communicate with each other and the port b and the port c to communicate with each other. The control units of the indoor units 8a to 8e open the first electromagnetic valves 61a to 61e of the corresponding flow dividing units 6a to 6e and close the second electromagnetic valves 62a to 62e. Thereby, the outdoor heat exchanger 23 becomes an evaporator, and all the indoor heat exchangers 81a to 81e of the indoor units 8a to 8e become condensers.

  The high-pressure refrigerant discharged from the compressor 21 flows through the high-pressure gas pipe 30 and flows into the diversion units 6a to 6e. The high-pressure refrigerant that has flowed into the diversion units 6a to 6e flows through the first diversion pipes 63a to 63e provided with the open first electromagnetic valves 61a to 61e, and flows out from the diversion units 6a to 6e. It flows into the indoor units 8a to 8e.

  The high-pressure refrigerant that has flowed into the indoor units 8a to 8e flows into the indoor heat exchangers 81a to 81e, exchanges heat with the indoor air, and condenses, thereby heating the room in which the indoor units 8a to 8e are installed. Done. The high-pressure refrigerant that has flowed out of the indoor heat exchangers 81a to 81e passes through the indoor expansion valves 82a to 82e and is depressurized. Here, the indoor expansion valves 82a to 82e are the refrigerant temperature detected by the liquid side temperature sensors 84a to 84e and the high pressure saturation temperature obtained from the outdoor unit 2 (the high pressure sensor of the outdoor unit 2). Calculated from the pressure of the refrigerant detected at 50, the temperature corresponding to the condensation temperature in the indoor heat exchangers 81a to 81e), and the degree of refrigerant subcooling at the outlets of the indoor heat exchangers 81a to 81e that are condensers. The opening is determined according to this.

  Specifically, in the case where the refrigerant flow rate is small with respect to the size of the heating capacity requested by the indoor units 8a to 8e and the degree of supercooling of the refrigerant at the outlets of the indoor heat exchangers 81a to 81e is large, The control units of the machines 8a to 8e increase the flow rates of the refrigerant by increasing the openings of the indoor expansion valves 82a to 82e. Further, in the case where the refrigerant flow rate is large with respect to the size of the heating capacity requested by the indoor units 8a to 8e, and accordingly, the degree of supercooling of the refrigerant at the outlets of the indoor heat exchangers 81a to 81e is small, The control units of the indoor units 8a to 8e reduce the flow rate of the refrigerant by reducing the opening degrees of the indoor expansion valves 82a to 82e.

  The intermediate-pressure refrigerant that has flowed out of the indoor units 8 a to 8 e flows into the liquid pipe 32. The intermediate-pressure refrigerant that has flowed into the outdoor unit 2 through the closing valve 44 is reduced in pressure when passing through the outdoor expansion valve 40 having an opening degree corresponding to the degree of superheat at the outlet of the outdoor heat exchanger 23. It becomes a low-pressure refrigerant and flows into the outdoor heat exchanger 23. The low-pressure refrigerant that has flowed into the outdoor heat exchanger 23 evaporates by exchanging heat with the outside air. Then, the low-pressure refrigerant that has flowed out of the outdoor heat exchanger 23 passes through the four-way valve 22, then passes through the accumulator 24, is sucked into the compressor 21, and is compressed again.

  Next, the case where the cooling / heating-free operation is performed will be described. In the following description of the air-conditioning-free operation, as shown in FIG. 3, the load required by the three indoor units 8 a to 8 c performing the air-cooling operation performs the air-warming operation. A case where the load is larger than that required by the two indoor units 8d and 8e will be described as an example. Further, in the case of performing the heating main operation, as shown in FIG. 4, the loads required by the three indoor units 8 a to 8 c performing the heating operation are the two indoor units performing the cooling operation. A case where the load is larger than the load required in 8d and 8e will be described as an example.

  First, the case where the cooling main operation is performed will be described with reference to FIG. In FIG. 3, the arrow indicates the flow of the refrigerant. As shown in FIG. 3, in this operation, the control unit 100 sets the port a and the port b of the four-way valve 22 to communicate with each other and the port c and the port d to communicate with each other. Thereby, the outdoor heat exchanger 23 becomes a condenser.

  Further, the control units of the three indoor units 8a to 8c that perform the cooling operation close the first electromagnetic valves 61a to 61c of the corresponding three branch units 6a to 6c to shut off the first branch pipes 63a to 63c. At the same time, the second electromagnetic valves 62a to 62c are opened to connect the second branch pipes 64a to 64c. Thereby, the indoor heat exchangers 81a to 81c of the three indoor units 8a to 8c are evaporators.

  On the other hand, the control units of the two indoor units 8d and 8e that perform the heating operation open the first electromagnetic valves 61d and 61e of the corresponding two branch units 6d and 6e to communicate the first branch pipes 63d and 63e. At the same time, the second electromagnetic valves 62d and 62e are closed to shut off the second branch pipes 64d and 64e. Thereby, the indoor heat exchangers 81d and 81e of the two indoor units 8d and 8e become condensers.

  The high-pressure refrigerant discharged from the compressor 21 is divided into the four-way valve 22 side and the high-pressure gas pipe 30 side. The high-pressure refrigerant that has passed through the four-way valve 22 flows into the outdoor heat exchanger 23 and exchanges heat with the outside air to condense. The refrigerant condensed in the outdoor heat exchanger 23 passes through the outdoor expansion valve 40 having an opening degree corresponding to the difference between the discharge pressure and the hydraulic pressure of the compressor 21 taken in by the control unit 100, and is an intermediate pressure refrigerant. Then, the liquid flows through the liquid pipe 32 and flows into the indoor units 8a to 8c.

  The intermediate-pressure refrigerant that has flowed into the indoor units 8a to 8c is decompressed by the indoor expansion valves 82a to 82c, becomes low-pressure refrigerant, and flows into the indoor heat exchangers 81a to 81c. The low-pressure refrigerant that has flowed into the indoor heat exchangers 81a to 81c evaporates by exchanging heat with room air, thereby cooling the room where the indoor units 8a to 8c are installed. Here, the indoor expansion valves 82a to 82c are the evaporators based on the refrigerant temperature detected by the liquid side temperature sensors 84a to 84c and the refrigerant temperature detected by the gas side temperature sensors 85a to 85c by the control unit of the indoor units 8a to 8c. The degree of superheat of the refrigerant in the indoor heat exchangers 81a to 81c is obtained, and the opening degree is determined accordingly. Since the relationship between the degree of superheat and the opening degree of the indoor expansion valves 82a to 82c is the same as that described in the case of performing the cooling operation, the description thereof is omitted.

  The low-pressure refrigerant that has flowed out of the indoor heat exchangers 81a to 81c flows into the diversion units 6a to 6c, and flows through the second diversion pipes 64a to 64c provided with the open second electromagnetic valves 62a to 62c to low pressure. It flows into the gas pipe 31. The low-pressure refrigerant that has flowed into the low-pressure gas pipe 31 from each of the diversion units 6a to 6c merges in the low-pressure gas pipe 31, and then flows into the outdoor unit 2, passes through the accumulator 24, and is sucked into the compressor 21. It is compressed again.

  On the other hand, the high-pressure refrigerant flowing through the high-pressure gas pipe 30 and flowing into the diversion units 6d and 6e flows through the first diversion pipes 63d and 63e provided with the first electromagnetic valves 61d and 61e that are open, and passes through the indoor unit. It flows into 8d and 8e. The high-pressure refrigerant that has flowed into the indoor units 8d and 8e flows into the indoor heat exchangers 81d and 81e, exchanges heat with the indoor air, and condenses, thereby heating the room in which the indoor units 8d and 8e are installed. Done. The high-pressure refrigerant that has flowed out of the indoor heat exchangers 81d and 81e passes through the indoor expansion valves 82d and 82e and is reduced in pressure to become an intermediate-pressure refrigerant.

  Here, the indoor expansion valves 82d and 82e are indoor units that are condensers based on the refrigerant temperature detected by the liquid side temperature sensors 84d and 84e and the high-pressure saturation temperature obtained from the outdoor unit 2 by the control unit of the indoor units 8d and 8e. The degree of refrigerant supercooling in the heat exchangers 81d and 81e is obtained, and the opening degree is determined accordingly. Since the relationship between the degree of supercooling and the opening degree of the indoor expansion valves 82d and 82e is the same as that described in the case of performing the heating operation, the description thereof is omitted.

  The intermediate-pressure refrigerant that has flowed out of the indoor units 8d and 8e and merged in the liquid pipe 32 is condensed in the outdoor heat exchanger 23, depressurized by the outdoor expansion valve, and flows out of the outdoor unit 2 to the liquid pipe 32.

  Next, the case where the heating main operation is performed will be described with reference to FIG. In FIG. 4, the arrows indicate the flow of the refrigerant. As shown in FIG. 4, in this operation, the control unit 100 sets the port a and the port d of the four-way valve 22 to communicate with each other and the port b and the port c to communicate with each other. Thereby, the outdoor heat exchanger 23 becomes an evaporator.

  Further, the control units of the three indoor units 8a to 8c that perform the heating operation open the first electromagnetic valves 61a to 61c of the corresponding three branch units 6a to 6c to communicate the first branch pipes 63a to 63c. At the same time, the second solenoid valves 62a to 62c are closed to shut off the second branch pipes 64a to 64c. Thereby, the indoor heat exchangers 81a to 81c of the three indoor units 8a to 8c become condensers.

  On the other hand, the control units of the two indoor units 8d and 8e that perform the cooling operation close the first electromagnetic valves 61d and 61e of the corresponding two branch units 6d and 6e, and shut off the first branch pipes 63d and 63e. At the same time, the second electromagnetic valves 62d and 62e are opened to communicate the second branch pipes 64d and 64e. Thereby, the indoor heat exchangers 81d and 81e of the two indoor units 8d and 8e become evaporators.

  The high-pressure refrigerant discharged from the compressor 21 flows through the high-pressure gas pipe 30 and flows into the diversion units 6a to 6c. The high-pressure refrigerant that has flowed into the diversion units 6a to 6c flows through the first diversion pipes 63a to 63c provided with the open first electromagnetic valves 61a to 61c, and flows out from the diversion units 6a to 6c. It flows into the indoor units 8a to 8c.

  The high-pressure refrigerant flowing into the indoor units 8a to 8c flows into the indoor heat exchangers 81a to 81c, exchanges heat with the indoor air, and condenses, thereby heating the room where the indoor units 8a to 8c are installed. Done. The high-pressure refrigerant condensed in the indoor heat exchangers 81a to 81c passes through the indoor expansion valves 82a to 82c and is reduced in pressure to become an intermediate-pressure refrigerant. Here, the indoor expansion valves 82 a to 82 c are indoors that are condensers from the refrigerant temperature detected by the liquid side temperature sensors 84 a to 84 c and the high-pressure saturation temperature obtained from the outdoor unit 2 by the control units of the indoor units 8 a to 8 c. The degree of refrigerant supercooling in the heat exchangers 81a to 81c is obtained, and the opening degree is determined accordingly. The relationship between the degree of supercooling and the openings of the indoor expansion valves 82a to 82c is the same as that described in the case of performing the heating operation as described above, and thus the description thereof is omitted.

  The intermediate-pressure refrigerant that has flowed out of the indoor units 8 a to 8 c flows into the liquid pipe 32. Then, a part of the intermediate-pressure refrigerant merged in the liquid pipe 32 flows into the outdoor unit 2, and the rest flows through the liquid pipe 32 and flows into the indoor units 8d and 8e. The intermediate-pressure refrigerant flowing into the outdoor unit 2 is reduced in pressure when passing through the outdoor expansion valve 40 having an opening degree corresponding to the degree of superheat of the outdoor heat exchanger 23 to become a low-pressure refrigerant. Flow into. The low-pressure refrigerant that has flowed into the outdoor heat exchanger 23 evaporates by exchanging heat with the outside air. Then, the low-pressure refrigerant that has flowed out of the outdoor heat exchanger 23 passes through the four-way valve 22, then passes through the accumulator 24, is sucked into the compressor 21, and is compressed again.

  On the other hand, the intermediate-pressure refrigerant flowing into the indoor units 8d and 8e is decompressed by the indoor expansion valves 82d and 82e to become a low-pressure refrigerant and flows into the indoor heat exchangers 81d and 81e. The low-pressure refrigerant that has flowed into the indoor heat exchangers 81d and 81e exchanges heat with the indoor air and evaporates, thereby cooling the room in which the indoor units 8d and 8e are installed. Here, the indoor expansion valves 82d and 82e are evaporators based on the refrigerant temperature detected by the liquid side temperature sensors 84d and 84e and the refrigerant temperature detected by the gas side temperature sensors 85d and 85e by the control unit of the indoor units 8d and 8e. The degree of superheat of the refrigerant in the indoor heat exchangers 81d and 81e is obtained, and the opening degree is determined accordingly. Since the relationship between the degree of superheat and the opening degree of the indoor expansion valves 82d and 82e is the same as that described in the case of performing the cooling operation, the description thereof is omitted.

  The low-pressure refrigerant that has flowed out of the indoor heat exchangers 81d and 81e flows into the diversion units 6d and 6e, and flows through the second diversion pipes 64d and 64e provided with the open second electromagnetic valves 62d and 62e to low pressure. It flows into the gas pipe 31. The low-pressure refrigerant flowing into the low-pressure gas pipe 31 from each of the branch units 6d and 6e joins in the low-pressure gas pipe 31, and then flows into the outdoor unit 2, passes through the accumulator 24, and is sucked into the compressor 21. It is compressed again.

  Next, using FIG. 5 and FIG. 6, the liquid pipe 32 is controlled by controlling the pressure of the refrigerant flowing through the liquid pipe 32 when the air-conditioning apparatus 1 according to the present embodiment performs the cooling and heating-free operation. About a method of ensuring a pressure difference between the pressure of the flowing refrigerant and the pressure of the refrigerant flowing through the high-pressure gas pipe 30 or the low-pressure gas pipe 31, and preventing a decrease in the amount of refrigerant circulation in the indoor unit performing the cooling operation or the heating operation. This will be specifically described.

  First, the case where the outdoor heat exchanger 23 is a condenser when the air-conditioning apparatus 1 performs an air-conditioning-free operation will be described with reference to FIG. Note that FIG. 5 has the same configuration as the refrigerant circuit during the cooling main operation described in FIG. 3, and thus detailed description thereof will be omitted, and only an explanation regarding the pressure control of the refrigerant flowing through the liquid pipe 32 will be given. Moreover, in the following description, high cooling capacity is required in the indoor unit 8a among the three indoor units 8a to 8c performing the cooling operation, and the pressure of the refrigerant flowing through the liquid pipe 32 (hereinafter referred to as liquid pressure). And when the pressure difference between the refrigerant flowing through the low pressure gas pipe 31 (hereinafter referred to as “low pressure”) becomes small and the heating capacity of the indoor unit 8d out of the two indoor units 8d and 8e performing the heating operation is high. Is described, and the pressure difference between the pressure of the refrigerant flowing through the high-pressure gas pipe 30 (hereinafter referred to as “high pressure”) and the liquid pressure is reduced. In addition, when the front and rear of each indoor expansion valve are described, the side where the refrigerant flows into each indoor expansion valve is the front side of each indoor expansion valve, and the side where the refrigerant flows out from each indoor expansion valve is the side of each indoor expansion valve. The back side, and so on.

  First, the case where a high cooling capacity is required in the indoor unit 8a and the pressure difference between the hydraulic pressure and the low pressure becomes small will be described. In the state of the refrigerant circuit shown in FIG. 5, when a high cooling capacity is required in the indoor unit 8a that is performing the cooling operation, the control unit of the indoor unit 8a sends the indoor heat exchanger 81a to the indoor heat exchanger 81a according to the required cooling capacity. In order to increase the amount of refrigerant flowing, control is performed to increase the opening of the indoor expansion valve 82a.

  When the opening of the indoor expansion valve 82a increases, the pressure difference between the hydraulic pressure and the low pressure, that is, the liquid pipe 32 side (front side of the indoor expansion valve 82a) and the low pressure gas pipe 31 side (indoor expansion valve 82a) of the indoor expansion valve 82a. The pressure difference from the rear side becomes smaller. When the pressure difference between the hydraulic pressure (intermediate pressure) and the low pressure becomes smaller than a predetermined value (for example, 0.5 MPa), the amount of refrigerant flowing through the indoor heat exchanger 81a decreases. The other indoor units 8b and 8c performing the cooling operation are connected by pipes in parallel with the indoor unit 8a, and the indoor units 8a to 8c are connected to the low-pressure gas pipe 31, respectively. When the pressure difference before and after 82a becomes smaller than a predetermined value, the amount of refrigerant flowing through the indoor heat exchangers 81b and 81c of the indoor units 8b and 8c also decreases.

  On the other hand, as described above, when the pressure difference before and after the indoor expansion valve 82a is smaller than a predetermined value, that is, when the pressure difference between the hydraulic pressure and the low pressure is smaller than the predetermined value, the refrigerant circulation amount in the indoor units 8a to 8c is increased. The amount of refrigerant circulating in the indoor units 8a to 8c cannot be ensured, and there is a possibility that the cooling capacity required for the indoor units 8a to 8c performing the cooling operation cannot be exhibited.

  When the above state is reached, the control unit 100 opens or fully closes the first expansion valve 41 and the second expansion valve 42 at a predetermined opening degree, thereby causing the first bypass pipe 33 and the second bypass pipe 34 to open. By connecting or shutting off the refrigerant so that a predetermined amount of refrigerant flows, the hydraulic pressure is increased, and the pressure difference between the hydraulic pressure and the low pressure is set to a predetermined value or more, thereby ensuring the refrigerant circulation amount in the indoor units 8a to 8c. Control as much as possible.

  Specifically, the CPU 110 of the control unit 100 is the liquid refrigerant pressure that is the liquid pressure before the indoor expansion valve 82 a detected by the intermediate pressure sensor 57 and the low pressure after the indoor expansion valve 82 a that is detected by the low pressure sensor 51. The low-pressure refrigerant pressure is taken in periodically and stored in the storage unit 120. The CPU 110 calculates a pressure difference between the stored liquid pipe refrigerant pressure and the low pressure refrigerant pressure. When this pressure difference is smaller than a predetermined value, the CPU 110 shuts off the second bypass pipe 34 by closing the second expansion valve 42 (or keeping the fully closed state in the initial setting), and The expansion valve 41 is opened at a predetermined opening to allow the first bypass pipe 33 to communicate.

  A part of the refrigerant discharged from the compressor 21 and flowing to the high-pressure gas pipe 30 as shown by an arrow A in FIG. 5 by opening the first expansion valve 41 at a predetermined opening and communicating the first bypass pipe 33. Flows into the liquid pipe 32. Thereby, since the hydraulic pressure increases, the pressure difference between the hydraulic pressure and the low pressure can be set to a predetermined value or more. Therefore, the refrigerant circulation amount in the indoor units 8a to 8c can be secured, and the shortage of the cooling capacity can be suppressed in the indoor units 8a to 8c performing the cooling operation.

  Next, the case where high heating capacity is required in the indoor unit 8d and the pressure difference between the high pressure and the hydraulic pressure is reduced will be described. In the state of the refrigerant circuit shown in FIG. 5, when a high heating capacity is required in the indoor unit 8d that is performing the heating operation, the control unit of the indoor unit 8d sends the indoor heat exchanger 81d to the indoor heat exchanger 81d according to the required heating capacity. In order to increase the amount of refrigerant flowing, control is performed to increase the opening of the indoor expansion valve 82d.

  When the opening of the indoor expansion valve 82d increases, the pressure difference between the high pressure and the hydraulic pressure, that is, the high-pressure gas pipe 30 side of the indoor expansion valve 82d (the front side of the indoor expansion valve 82d) and the liquid pipe 32 side (the indoor expansion valve 82d). The pressure difference from the rear side becomes smaller. When the pressure difference between the high pressure and the fluid pressure (intermediate pressure) becomes smaller than a predetermined value (for example, 0.5 MPa), the amount of refrigerant flowing through the indoor heat exchanger 81d decreases. The other indoor unit 8e that performs the heating operation is connected to the indoor unit 8d in parallel, and the indoor units 8d and 8e are connected to the high-pressure gas pipe 30, respectively. If the pressure difference before and after becomes smaller than a predetermined value, the amount of refrigerant flowing through the indoor heat exchanger 81e of the indoor unit 8e also decreases.

  On the other hand, as described above, when the pressure difference before and after the indoor expansion valve 82d is smaller than a predetermined value, that is, when the pressure difference between the high pressure and the hydraulic pressure is smaller than the predetermined value, the refrigerant circulation amount in the indoor units 8d and 8e is increased. The amount of refrigerant circulating in the indoor units 8d and 8e cannot be ensured, and there is a possibility that the heating capacity required by the indoor units 8d and 8e that are performing the heating operation cannot be exhibited.

  When the above state is reached, the control unit 100 opens or fully closes the first expansion valve 41 and the second expansion valve 42 at a predetermined opening degree, thereby causing the first bypass pipe 33 and the second bypass pipe 34 to open. By connecting or blocking the refrigerant so that a predetermined amount of refrigerant flows, the hydraulic pressure is lowered, and the pressure difference between the high pressure and the hydraulic pressure is set to a predetermined value or more, thereby ensuring the refrigerant circulation amount in the indoor units 8d and 8e. Control as much as possible.

  Specifically, the CPU 110 of the control unit 100 detects the high pressure refrigerant pressure detected by the high pressure sensor 50 before the indoor expansion valve 82d and the liquid pressure detected by the intermediate pressure sensor 57 after the indoor expansion valve 82a. The pipe refrigerant pressure is periodically taken in and stored in the storage unit 120. The CPU 110 calculates the pressure difference between the stored high-pressure refrigerant pressure and the liquid pipe refrigerant pressure. When this pressure difference is smaller than a predetermined value, the CPU 110 shuts off the first bypass pipe 33 by closing the first expansion valve 41 (or keeping the initial setting in the fully closed state) and the second The expansion valve 42 is opened at a predetermined opening to allow the second bypass pipe 34 to communicate.

  By opening the second expansion valve 42 at a predetermined opening and communicating the second bypass pipe 34, a part of the refrigerant flowing through the liquid pipe 32 flows into the low-pressure gas pipe 31 as indicated by an arrow B in FIG. 5. To do. Thereby, since the liquid pipe refrigerant pressure is lowered, the pressure difference between the high pressure and the liquid pressure can be set to a predetermined value or more. Therefore, the refrigerant circulation amount in the indoor units 8d and 8e can be secured, and the shortage of the heating capacity can be suppressed in the indoor units 8d and 8e performing the heating operation.

  Next, the case where the outdoor heat exchanger 23 is an evaporator when the air-conditioning apparatus 1 performs an air-conditioning-free operation will be described with reference to FIG. 6 has the same configuration as that of the refrigerant circuit during the heating-main operation described in FIG. 4, detailed description thereof will be omitted, and only description of pressure control of the refrigerant flowing through the liquid pipe 32 will be given. Moreover, in the following description, when the indoor unit 8a requires a high heating capacity among the three indoor units 8a to 8c performing the heating operation, and the pressure difference between the high pressure and the hydraulic pressure is small, the cooling operation A case will be described in which a high cooling capacity is required in the indoor unit 8d out of the two indoor units 8d and 8e, and the pressure difference between the hydraulic pressure and the low pressure becomes small. Similarly to the description in FIG. 5, when it is described before and after each indoor expansion valve, the side into which the refrigerant flows into each indoor expansion valve is the front side of each indoor expansion valve, and the refrigerant flows from each indoor expansion valve. The outflow side is the rear side of each indoor expansion valve.

  First, the case where high heating capacity is required in the indoor unit 8a and the pressure difference between the high pressure and the hydraulic pressure is reduced will be described. In the state of the refrigerant circuit shown in FIG. 6, when a high heating capacity is required in the indoor unit 8a that is performing the heating operation, the control unit of the indoor unit 8a sends the indoor heat exchanger 81a to the indoor heat exchanger 81a according to the required heating capacity. In order to increase the amount of refrigerant flowing, control is performed to increase the opening of the indoor expansion valve 82a.

  When the opening of the indoor expansion valve 82a increases, the pressure difference between the high pressure and the hydraulic pressure, that is, the high-pressure gas pipe 30 side of the indoor expansion valve 82a (the front side of the indoor expansion valve 82a) and the liquid pipe 32 side (the indoor expansion valve 82a). The pressure difference from the rear side becomes smaller. When the pressure difference between the high pressure and the hydraulic pressure (intermediate pressure) becomes smaller than a predetermined value (for example, 0.5 MPa), the amount of refrigerant flowing through the indoor heat exchanger 81a decreases. The other indoor units 8b and 8c performing the heating operation are connected to the indoor unit 8a in parallel, and the indoor units 8a to 8c are connected to the high-pressure gas pipe 30, respectively. When the pressure difference before and after 82a becomes smaller than a predetermined value, the amount of refrigerant flowing through the indoor heat exchangers 81b and 81c of the indoor units 8b and 8c also decreases.

  On the other hand, as described above, when the pressure difference before and after the indoor expansion valve 82a is smaller than a predetermined value, that is, when the pressure difference between the high pressure and the hydraulic pressure is smaller than the predetermined value, the refrigerant circulation amount in the indoor units 8a to 8c is increased. The amount of refrigerant circulating in the indoor units 8a to 8c cannot be ensured, and the heating capacity required for the indoor units 8a to 8c performing the heating operation may not be exhibited.

  When the above state is reached, the control unit 100 opens or fully closes the first expansion valve 41 and the second expansion valve 42 at a predetermined opening degree, thereby causing the first bypass pipe 33 and the second bypass pipe 34 to open. The indoor units 8a to 8c are configured to reduce the pressure of the refrigerant flowing through the liquid pipe 32 by connecting or blocking the refrigerant so that a predetermined amount of refrigerant flows, and to set the pressure difference between the high pressure and the hydraulic pressure to a predetermined value or more. Control is performed so as to ensure a sufficient amount of refrigerant circulation.

  Specifically, the CPU 110 of the control unit 100 detects the high-pressure refrigerant pressure that is high before the indoor expansion valve 82 a detected by the high-pressure sensor 50 and the liquid pressure that is after the indoor expansion valve 82 a that is detected by the intermediate pressure sensor 57. The pipe refrigerant pressure is periodically taken in and stored in the storage unit 120. The CPU 110 calculates the pressure difference between the stored high-pressure refrigerant pressure and the liquid pipe refrigerant pressure. When this pressure difference is smaller than a predetermined value, the CPU 110 shuts off the first bypass pipe 33 by closing the first expansion valve 41 (or keeping the initial setting in the fully closed state) and the second The expansion valve 42 is opened at a predetermined opening to allow the second bypass pipe 34 to communicate.

By opening the second expansion valve 42 at a predetermined opening and communicating the second bypass pipe 34, the arrow C in FIG.
As shown, a part of the refrigerant flowing through the liquid pipe 32 flows into the low-pressure gas pipe 31. Thereby, since the liquid pipe refrigerant pressure is lowered, the pressure difference between the high pressure refrigerant pressure and the liquid pipe refrigerant pressure can be set to a predetermined value or more. Therefore, the refrigerant circulation amount in the indoor units 8a to 8c can be ensured, and the shortage of the heating capacity can be suppressed in the indoor units 8a to 8c performing the heating operation.

  Next, a case where a high cooling capacity is required in the indoor unit 8d and the pressure difference between the hydraulic pressure and the low pressure becomes small will be described. In the state of the refrigerant circuit shown in FIG. 6, when a high cooling capacity is required in the indoor unit 8d that is performing the cooling operation, the control unit of the indoor unit 8d sends the indoor heat exchanger 81d to the indoor heat exchanger 81d according to the required cooling capacity. In order to increase the amount of refrigerant flowing, control is performed to increase the opening of the indoor expansion valve 82d.

  When the opening of the indoor expansion valve 82d increases, the pressure difference between the hydraulic pressure and the low pressure, that is, the liquid pipe 32 side (the front side of the indoor expansion valve 82d) and the low pressure gas pipe 31 side (the indoor expansion valve 82d) of the indoor expansion valve 82d. The pressure difference from the front side) becomes smaller. When the pressure difference between the hydraulic pressure (intermediate pressure) and the low pressure becomes smaller than a predetermined value (for example, 0.5 MPa), the amount of refrigerant flowing through the indoor heat exchanger 81d decreases. The other indoor unit 8e performing the cooling operation is connected to the indoor unit 8d in parallel, and the indoor units 8d and 8e are connected to the low-pressure gas pipe 31, respectively. If the pressure difference before and after becomes smaller than a predetermined value, the amount of refrigerant flowing through the indoor heat exchanger 81e of the indoor unit 8e also decreases.

  On the other hand, as described above, when the pressure difference before and after the indoor expansion valve 82d is smaller than a predetermined value, that is, when the pressure difference between the hydraulic pressure and the low pressure is smaller than the predetermined value, the refrigerant circulation amount in the indoor units 8d and 8e is increased. The amount of refrigerant circulating in the indoor units 8d and 8e cannot be ensured, and the cooling capacity required for the indoor units 8d and 8e performing the cooling operation may not be exhibited.

  When the above state is reached, the control unit 100 opens or fully closes the first expansion valve 41 and the second expansion valve 42 at a predetermined opening degree, thereby causing the first bypass pipe 33 and the second bypass pipe 34 to open. By connecting or blocking the refrigerant so that a predetermined amount of refrigerant flows, the pressure of the refrigerant flowing through the liquid pipe 32 is increased, and the pressure difference between the liquid pressure and the low pressure is set to a predetermined value or more, so that the indoor units 8d and 8e Control is performed so as to ensure a sufficient amount of refrigerant circulation.

  Specifically, the CPU 110 of the control unit 100 is the liquid refrigerant pressure that is the fluid pressure before the indoor expansion valve 82 a detected by the intermediate pressure sensor 57 and the low pressure after the indoor expansion valve 82 d that is detected by the low pressure sensor 51. The low-pressure refrigerant pressure is taken in periodically and stored in the storage unit 120. The CPU 110 calculates a pressure difference between the stored liquid pipe refrigerant pressure and the low pressure refrigerant pressure. When this pressure difference is smaller than a predetermined value, the CPU 110 shuts off the second bypass pipe 34 by closing the second expansion valve 42 (or keeping the fully closed state in the initial setting), and The expansion valve 41 is opened at a predetermined opening to allow the first bypass pipe 33 to communicate.

  By opening the first expansion valve 41 at a predetermined opening and communicating the first bypass pipe 33, a part of the refrigerant flowing through the high-pressure gas pipe 30 flows into the liquid pipe 32 as shown by an arrow D in FIG. To do. Thereby, since the liquid pipe refrigerant pressure increases, the pressure difference between the liquid pipe refrigerant pressure and the low pressure refrigerant pressure can be set to a predetermined value or more. Therefore, the refrigerant circulation amount in the indoor units 8d and 8e can be secured, and the shortage of the cooling capacity can be suppressed in the indoor units 8d and 8e performing the cooling operation.

  In the embodiment described above, the case where three of the five indoor units are performing the cooling operation as an example of the cooling main operation when the air conditioner 1 is performing the cooling-free operation is described. However, regardless of the number of indoor units performing the cooling operation, if the load on the indoor unit performing the cooling operation is greater than the load on the indoor unit performing the heating operation, the cooling main operation is performed. .

  In addition, as an example of the heating main operation, the case where three of the five indoor units are performing the heating operation has been described. However, the heating operation is performed regardless of the number of indoor units performing the heating operation. If the load on the existing indoor unit is greater than the load on the indoor unit performing the cooling operation, the heating main operation is performed.

  Further, the pressure difference between the liquid pipe 32 side of the indoor expansion valves 82a to 82e and the high pressure gas pipe 30 side or the low pressure gas pipe 31 side is such that the gas pipe side of the indoor expansion valves 82a to 82e is the high pressure gas pipe 30 or low pressure gas pipe 31. Regardless of the case, the case where the same predetermined value is set to perform the control has been described, but the case where the gas pipe side of the indoor expansion valves 82a to 82e is the high pressure gas pipe 30 and the case where the low pressure gas pipe 31 is used. For example, the high pressure gas pipe 30 may be set to 0.5 MPa, and the low pressure gas pipe 31 may be set to 1.0 MPa.

  Further, the high pressure sensor 50 detects the high pressure, the low pressure sensor 51 detects the low pressure, and the intermediate pressure sensor 57 detects the hydraulic pressure, and the pressure difference between the high pressure and the hydraulic pressure or the pressure difference between the hydraulic pressure and the low pressure is less than a predetermined value. In this case, the case where the hydraulic pressure is controlled by controlling the opening and closing of the first expansion valve 41 and the second expansion valve 42 has been described. The liquid pipe refrigerant pressure may be controlled by controlling the opening and closing of the first expansion valve 41 and the second expansion valve 42 according to the difference.

  Specifically, the control unit 100 detects the pressure of the refrigerant flowing through the high-pressure gas pipe 30 with the high-pressure sensor 50, and calculates the saturation temperature corresponding to the detected high pressure, so that the indoor heat exchanger that is a condenser Or the condensation temperature in an outdoor heat exchanger is calculated | required. The control unit 100 and the high-pressure sensor 50 constitute a condensation temperature detection unit. Moreover, the control part 100 takes in the evaporation temperature of the indoor exchanger detected by the liquid side temperature sensor of the indoor unit which is performing the cooling operation. In this case, the liquid side temperature sensor of the indoor unit performing the cooling operation serves as the evaporation temperature detecting means. Further, the control unit 100 detects the temperature of the refrigerant flowing through the liquid pipe 32 (hereinafter referred to as “liquid pipe refrigerant temperature”) by the refrigerant temperature sensor 54. The refrigerant temperature sensor 54 is a liquid pipe refrigerant temperature detecting means.

  Since the condensation temperature changes in response to a change in high pressure, it is an index indicating the pressure of the refrigerant flowing through the high pressure gas pipe 30. Further, since the evaporation temperature changes in response to a change in low pressure, it becomes an index indicating the pressure of the refrigerant flowing through the low pressure gas pipe 31. Therefore, the control unit 100 grasps the pressure difference between the liquid pressure and the high pressure or the low pressure by calculating the temperature difference between the condensing temperature and the liquid pipe refrigerant temperature and the temperature difference between the liquid pipe refrigerant temperature and the evaporation temperature. Can do.

  When the air conditioner 1 is performing air-conditioning-free operation, the control unit 100 calculates a temperature difference between the detected condensation temperature and the liquid pipe refrigerant temperature, or a temperature difference between the liquid pipe refrigerant temperature and the evaporation temperature. When this temperature difference becomes smaller than a predetermined value, the second expansion valve 42 is fully closed to shut off the second bypass pipe 34, and the first expansion valve 41 is opened at a predetermined opening degree to open the first bypass pipe. 33, or the first expansion valve 41 is fully closed to shut off the first bypass pipe 33, and the second expansion valve 42 is opened at a predetermined opening to allow the second bypass pipe 34 to communicate.

  As a result, the hydraulic pressure is increased or decreased, and the pressure difference between the high pressure and the low pressure and the hydraulic pressure can be set to a predetermined value or more. Therefore, it is possible to secure the refrigerant circulation amount in the indoor unit that is performing the cooling operation or the heating operation, and it is possible to suppress the shortage of the operation capability in each indoor unit.

  Next, the flow of processing in the air conditioner 1 according to the present invention will be described using the flowchart shown in FIG. The flowchart shown in FIG. 7 explains the flow of processing in the CPU 110 provided in the control unit 100 of the air conditioner 1. ST represents a step, and the subsequent numbers represent step numbers. In FIG. 7, the processing related to the present invention is mainly described, such as switching of the four-way valve 22, the rotation speed of the compressor corresponding to the set temperature instructed by the user, the opening degree adjustment of each expansion valve, etc. The description of other processes related to the refrigerant circuit is omitted.

  When the air conditioner 1 starts operation, the CPU 110 fully closes the first expansion valve 41 and the second expansion valve 42 of the outdoor unit 2 (ST1). Next, CPU 110 determines whether all the indoor units that are operating are performing a cooling operation or a heating operation (ST2).

  When all the indoor units being operated are performing a cooling operation or a heating operation (ST2-Yes), the CPU 110 detects the operation instruction contents (instructions such as the set temperature and the air volume) by the user and the detected values by various sensors. Accordingly, the operation of the outdoor unit 2 is started or continued (ST9). Then, the process returns to ST2.

  In ST2, when all the indoor units being operated are not performing the cooling operation or the heating operation (ST2-No), that is, in the case of performing the cooling-free operation, the CPU 110 detects the high-pressure refrigerant detected by the high-pressure sensor 50. The pressure, the low-pressure refrigerant pressure detected by the low-pressure sensor 51, and the liquid pipe refrigerant pressure detected by the intermediate pressure sensor 57 are taken in and stored in the storage unit 120 (ST3).

  Next, CPU 110 calculates a pressure difference between the stored high-pressure refrigerant pressure and liquid pipe refrigerant pressure, and determines whether this value is equal to or greater than a predetermined value (ST4). If the pressure difference is smaller than the predetermined value (ST4-No), the CPU 110 fully closes the first expansion valve 41 and opens the second expansion valve 42 at a predetermined opening (ST5). Then, the process proceeds to ST6.

  On the other hand, if the pressure difference is greater than or equal to a predetermined value in ST4 (ST4-Yes), CPU 110 calculates the pressure difference between the stored liquid pipe refrigerant pressure and the low-pressure refrigerant pressure, and whether or not this value is greater than or equal to the predetermined value. Is determined (ST10). If the pressure difference is equal to or greater than the predetermined value (ST10-Yes), CPU 110 returns the process to ST2. If the pressure difference is smaller than the predetermined value (ST10-No), the CPU 110 fully closes the second expansion valve 42 and opens the first expansion valve 41 at a predetermined opening (ST11). Then, the process proceeds to ST6.

  After controlling the opening and closing of the first expansion valve 41 and the second expansion valve 42 as described above, the CPU 110 determines the pressure difference between the high pressure refrigerant pressure and the liquid pipe refrigerant pressure or the liquid pipe refrigerant pressure and the low pressure refrigerant pressure. It is determined whether or not the pressure difference is equal to or greater than a predetermined value (ST6). If the pressure difference is not greater than or equal to the predetermined value (ST6-No), CPU 110 determines whether or not the current operating state has been changed (ST7).

  Here, the change in the operating state refers to a case where at least one of the current indoor units 8a to 8e is changed in operation mode. For example, three of the five indoor units are in the cooling operation. This is the case where the remaining state is changed from the state where the heating operation is performed to the state where the cooling operation is performed in all the indoor units.

  If the operating state has not been changed (ST7-No), CPU 110 returns the process to ST2. If the operating state has been changed (ST7-Yes), the CPU 110 fully closes the opened first expansion valve 41 or second expansion valve 42 (ST8), and returns the process to ST2. If the pressure difference is equal to or greater than the predetermined value in ST6 (ST6-Yes), the CPU 110 advances the process to ST8.

  When the operating state is changed in at least one indoor unit, the balance of pressure in the refrigerant circuit of the air conditioner 1 changes, and the pressure difference between the high pressure refrigerant pressure and the liquid pipe refrigerant pressure or the liquid pipe refrigerant pressure and the low pressure refrigerant pressure. The pressure difference with the also changes. Further, it is conceivable that all the indoor units 8a to 8e are in the cooling operation or the heating operation due to the change of the operation state, that is, the operation is not in the air conditioning / free operation. For the above reasons, in this embodiment, when the operating state is changed, the first expansion valve and the second expansion valve are once fully closed in the process of ST8, and the process from ST2 is repeated.

  As described above, in the air conditioner according to the present invention, the pressure of the refrigerant flowing through the liquid pipe is adjusted by opening and closing the flow rate adjustment valve of each bypass pipe. As a result, even when an outdoor heat exchanger is used as an evaporator, a high operating capacity is required in the indoor unit, and even if the difference between the hydraulic pressure and the low pressure or the difference between the high pressure and the hydraulic pressure becomes small These pressure differences can be ensured. Therefore, in the indoor unit that is performing the cooling operation or the heating operation, it is possible to prevent a decrease in the refrigerant circulation amount, and it is possible to suppress a shortage of the cooling capacity or the heating capability due to the decrease in the refrigerant circulation amount.

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 2 Outdoor unit 6a-6e Branch unit 8a-8e Indoor unit 21 Compressor 22 Four-way valve 23 Outdoor heat exchanger 30 High pressure gas pipe 31 Low pressure gas pipe 32 Liquid pipe 33 1st bypass pipe 34 2nd bypass pipe 40 Outdoor expansion valve 41 First expansion valve 42 Second expansion valve 50 High pressure sensor 51 Low pressure sensor 52 Discharge temperature sensor 53 Suction temperature sensor 54 Refrigerant temperature sensor 55 Heat exchanger temperature sensor 56 Outside air temperature sensor 57 Intermediate pressure sensor 61a to 61e First electromagnetic Valves 62a to 62e Second electromagnetic valves 63a to 63e First branch pipes 64a to 64e Second branch pipes 81a to 81e Indoor heat exchangers 82a to 82e Indoor expansion valves 84a to 84e Liquid side temperature sensors 85a to 85e Gas side temperature sensors 100 Control unit 110 CPU
120 storage unit 130 communication unit

Claims (2)

At least one outdoor unit including a compressor, an outdoor heat exchanger, and an outdoor expansion valve, a plurality of indoor units including the indoor heat exchanger, and a plurality of diversion units provided corresponding to the indoor unit And control means for controlling these, and a high-pressure gas pipe, a low-pressure gas pipe and a liquid pipe for connecting the outdoor unit, the plurality of indoor units and the plurality of diversion units to each other,
By switching the flow direction of the refrigerant in the plurality of indoor units by the diversion unit, an air conditioner capable of performing both cooling operation and heating operation in the plurality of indoor units,
A first pipe having a first flow rate control means is arranged to communicate a pipe connecting the discharge side of the compressor and the high pressure gas pipe and a pipe connecting the outdoor expansion valve and the liquid pipe. A bypass pipe,
A second pipe provided with a second flow rate control means is arranged to communicate between a pipe connecting the outdoor expansion valve and the liquid pipe and a pipe connecting the suction side of the compressor and the low pressure gas pipe. With a bypass pipe,
High-pressure refrigerant pressure detecting means for detecting high-pressure refrigerant pressure flowing through the high-pressure gas pipe, low-pressure refrigerant pressure detecting means for detecting low-pressure refrigerant pressure flowing through the low-pressure gas pipe, and liquid pipe refrigerant pressure flowing through the liquid pipe Liquid pipe refrigerant pressure detection means,
The control means calculates a pressure difference between the detected high pressure refrigerant pressure and the liquid pipe refrigerant pressure and a pressure difference between the liquid pipe refrigerant pressure and the low pressure refrigerant pressure, respectively, and calculates the calculated high pressure refrigerant pressure and the liquid pressure. When the pressure difference from the pipe refrigerant pressure or the pressure difference between the liquid pipe refrigerant pressure and the low-pressure refrigerant pressure is smaller than a predetermined value, the first flow rate control means and the second flow rate control means are An air conditioner characterized in that the pressure difference is adjusted to be equal to or greater than a predetermined value by controlling one of the first bypass pipe and the second bypass pipe and blocking the other. Instead of the high-pressure refrigerant pressure detecting means, the condensation temperature detecting means for detecting the condensation temperature in the indoor heat exchanger, which is a condenser, is replaced by the evaporator instead of the low-pressure refrigerant pressure detecting means. The evaporating temperature detecting means for detecting the evaporating temperature in the heat exchanger includes a liquid pipe refrigerant temperature detecting means for detecting the temperature of the liquid pipe refrigerant flowing in the liquid pipe instead of the liquid pipe refrigerant pressure detecting means,
The control means calculates a temperature difference between the detected condensation temperature and the liquid pipe refrigerant temperature and a temperature difference between the liquid pipe refrigerant temperature and the evaporation temperature, respectively, and calculates the calculated condensation temperature and the liquid pipe refrigerant temperature. Or the temperature difference between the liquid pipe refrigerant temperature and the evaporation temperature is smaller than a predetermined value, the first flow rate control means and the second flow rate control means are controlled to control the first flow rate control means. 2. The air conditioner according to claim 1, wherein the temperature difference is adjusted to be a predetermined value or more by individually communicating or blocking the first bypass pipe and the second bypass pipe.