JP4708371B2 - Air conditioner - Google Patents

Description

  The present invention generally relates to an air conditioner using a refrigeration cycle. In particular, the present invention includes a multi-room comprising a single outdoor unit and a plurality of indoor units, and a mode in which all the plurality of rooms are simultaneously cooled or heated, and a mode in which one room is cooled and another room is simultaneously heated. The present invention relates to a shape air conditioner.

  A conventional multi-room air conditioner includes an outdoor unit having a compressor and an outdoor heat exchanger, and a plurality of indoor units each having an indoor heat exchanger and a flow rate control valve, and includes the outdoor unit and the plurality of indoor units. Units are connected by inter-unit piping. One end of the indoor heat exchanger is alternatively connected to the refrigerant discharge port and the refrigerant suction port of the compressor by the first switching unit. The inter-unit piping includes a third inter-unit piping connected to the refrigerant discharge port side piping of the compressor, a first inter-unit piping connected to the refrigerant suction port side piping of the compressor, and outdoor heat exchange. And a second inter-unit pipe connected to the other end of the vessel. In the indoor unit, one end of the indoor heat exchanger is alternatively connected to the third inter-unit piping and the first inter-unit piping by the second switching unit, and the other end is connected to the second inter-unit piping. (For example, refer patent document 1).

  This conventional other room type air conditioner cools or heats all the rooms in which the indoor units are arranged (cooling operation mode and heating operation mode), and cools one room and simultaneously heats another room. There are two modes (a cooling main operation mode in which the cooling operation capacity is larger than the heating operation capacity and a heating main operation mode in which the heating operation capacity is larger than the cooling operation capacity).

In the cooling operation mode, all of the high-temperature and high-pressure gas refrigerant discharged from the compressor is changed to a high-density refrigerant by the outdoor heat exchanger, and is supplied to the indoor unit through the second inter-unit pipe. And the refrigerant | coolant supplied to the indoor unit changes into the refrigerant | coolant of a low-temperature low-pressure gas state with an indoor heat exchanger, returns to an outdoor heat exchanger from 1st unit piping through piping between 1st units.
In the heating operation mode, all of the high-temperature and high-pressure gaseous refrigerant discharged from the compressor is supplied to the indoor unit through the third inter-unit pipe. Then, the refrigerant supplied to the indoor unit changes to a low-temperature and low-pressure refrigerant in the indoor unit, and returns from the indoor unit to the outdoor heat exchanger through the second inter-unit pipe.

  In the cooling main operation mode, most of the refrigerant discharged from the compressor is changed to a high-density refrigerant by the outdoor heat exchanger, and supplied to the indoor unit that performs cooling through the second inter-unit pipe. The remaining refrigerant is supplied to the indoor unit that performs heating through the third inter-unit pipe in a high-temperature and high-pressure gas state, and after the temperature is lowered by the indoor heat exchanger, it merges with the refrigerant that flows through the second inter-unit pipe. And supplied to the indoor unit for cooling. The refrigerant supplied to the indoor unit that performs cooling is changed into a low-temperature and low-pressure gaseous refrigerant in the indoor heat exchanger, and returns to the outdoor unit through the first inter-unit pipe.

  In the heating main operation mode, most of the refrigerant discharged from the compressor is supplied to the indoor unit that performs heating through the third inter-unit pipe in a high-temperature and high-pressure gas state, and the temperature is lowered by the outdoor heat exchanger. The remaining refrigerant is changed to a high-density refrigerant by the outdoor heat exchanger, and is supplied to the indoor unit that performs cooling through the second inter-unit piping. Then, the refrigerant whose temperature has decreased in the indoor heat exchanger passes through the second inter-unit piping, merges with the refrigerant that has been changed to a high-density refrigerant in the outdoor heat exchanger, and is supplied to the indoor unit that performs cooling. The refrigerant supplied to the indoor unit that performs cooling is changed into a low-temperature and low-pressure gaseous refrigerant in the indoor heat exchanger, and returns to the outdoor unit through the first inter-unit pipe.

JP 2004-226018 A

In the conventional multi-chamber air conditioner, all of the high-temperature and high-pressure gas refrigerant discharged from the compressor flows through the third inter-unit piping in the heating operation mode, so that it can cope with the maximum heating capacity. In addition, it is necessary to increase the pipe diameter of the third inter-unit pipe.
Further, since the pipe diameter of the third inter-unit pipe is large, not only maintenance and pipe installation work become large, but also piping parts such as valves and strainers necessary for normal operation become large.
Furthermore, if the installation place of the outdoor unit and the indoor unit is separated from each other, the above problem becomes more remarkable.

  The present invention has been made to solve the above problems, and has a mode in which all of a plurality of rooms are simultaneously cooled or heated, and a mode in which one room is cooled and at the same time another room is heated. It aims at obtaining the air conditioning apparatus which can make the piping diameter of piping between units small, maintaining the performance similar to.

  An air conditioner according to the present invention includes an outdoor heat exchanger disposed to fluidly communicate between the first and second connection ends, a compressor that compresses and discharges refrigerant, and the outdoor heat exchanger. Fluid communication between the first switching unit that switches the direction of the flowing refrigerant, the outdoor unit having a third connection end connected to the discharge side of the compressor, and the first and second pipe connection units, respectively. A plurality of indoor units each having an indoor heat exchanger arranged to control the flow rate of the refrigerant flowing through the indoor heat exchanger, and each of the plurality of indoor units. A plurality of second switching portions for selectively connecting one pipe connection portion to either one of the first and second connection end portions, one end being connected to the first connection end portion, the other The ends of the plurality of second switching sections branch off A first inter-unit pipe connected to the first unit, one end connected to the second connection end, and the other end branched to connect between the second units connected to each of the plurality of second switching units Pipe, one end connected to the third connecting end, the other end connected to the second inter-unit pipe, a third inter-unit pipe, between the second inter-unit pipe and the third unit A third switching portion disposed at a connection portion with the pipe and selectively connecting the second switching portion to one of the second and third connection end portions; The first inter-unit pipe is connected to the second connection end of the third switching section, and the other end is branched and connected to the second pipe connection of each of the plurality of indoor units. And a second flow rate for controlling the flow rate of the refrigerant flowing through the first bypass pipeline Has a, a relay portion having a control unit.

  According to the present invention, since only a small amount of high-temperature and high-pressure refrigerant necessary for heating in the cooling-main operation flows through the third inter-unit pipe, a small-diameter pipe is used as the third inter-unit pipe. In addition, the piping parts can be miniaturized.

Embodiments of the present invention will be described below with reference to the drawings.
Embodiment 1 FIG.
1 is a refrigerant circuit diagram showing an air-conditioning apparatus according to Embodiment 1 of the present invention.
In FIG. 1, the air conditioner 2 includes an outdoor unit 4, a plurality of indoor units 6, and a relay unit 8 that connects the outdoor unit 4 and the indoor unit 6 with a refrigerant whose main component is carbon dioxide. In the first embodiment, the number of indoor units 6 is three (indoor units 6P, 6Q, 6R), but the present invention is not limited as long as the number is two or more. The air conditioner 2 is a cooling operation mode in which all the rooms in which the indoor units 6P to 6R are arranged are cooled, a heating operation mode in which all the rooms are heated, and another room is simultaneously heated. There are two modes (cooling main operation mode and heating main operation mode).

  The outdoor unit 4 includes a compressor 10 for compressing a refrigerant, a heat exchanger 12 as an outdoor heat exchanger, and a first switching unit 16, which are first and second connection end portions 20 a and 20 b. Are arranged in fluid communication with each other. The refrigerant discharge port 10a and the refrigerant suction port 10b of the compressor 10 are connected to the first switching unit 16 via pipes 14a and 14b, respectively. One end 12a of the heat exchanger 12 is connected to the first switching unit 16 via a pipe 14c. A pipe 14 d is also connected to the first switching unit 16. The pipe 14 d extends to the first connection end 20 a of the outdoor unit 4 to which one end of the first inter-unit pipe 18 a of the relay unit 8 is connected. The other end 12b of the heat exchanger 12 is connected to the pipe 14e. The pipe 14e extends to the second connection end 20b of the outdoor unit 4 to which one end of the second inter-unit pipe 18b of the relay unit 8 is connected. The refrigerant discharge port 10a of the compressor 10 is connected to the third connection end 20c of the outdoor unit 4 to which one end of the third inter-unit pipe 18c of the relay unit 8 is connected via the pipes 14a and 14f. ing. These 1st thru | or 3rd unit piping 18a, 18b, 18c is piping for connecting the outdoor unit 4 and the indoor units 6P-6R.

  The first switching unit 16 is configured to switch the direction of the refrigerant flowing in the heat exchanger 12 between the first and second flow states according to the operation mode. In the first flow state, the refrigerant is connected to the refrigerant suction port 10b of the compressor 10 from the first connection end 20a via the pipes 14d and 14b, and the refrigerant discharge port 10a of the compressor 10 is connected via the pipes 14a and 14c. Connected to one end 12 a of the heat exchanger 12. At this time, the refrigerant flows from one end 12a of the heat exchanger 12 to the other end 12b. On the other hand, in the second flow state, as shown in FIG. 3, one end 12a of the heat exchanger 12 is connected to the refrigerant suction port 10b of the compressor 10 via the pipes 14c and 14b, and the refrigerant discharge port of the compressor 10 is connected. 10a is connected to the first connection end 20a via the pipes 14a and 14d. At this time, the refrigerant flows from the other end 12b of the heat exchanger 12 to the one end 12a.

  The relay unit 8 has the same number of three-way switching valves 22 as second switching units having three connection ports 24a, 24b, and 24c as the indoor unit 6 (in the first embodiment, three of 22P, 22Q, and 22R). ) Prepare. One end of the first inter-unit pipe 18a is connected to the first connection end 20a, and the other end is branched and connected to the connection ports 24a of the three-way switching valves 22P to 22R. One end of the second inter-unit pipe 18b is connected to the second connection end 20b, and the other end is branched and connected to the connection ports 24b of the three-way switching valves 22P to 22R. Similarly, the connection port 24c is connected to the 1st piping connection part 26a of the corresponding indoor unit 6 via piping.

  The relay unit 8 also has a first bypass connected at one end in the middle of the second inter-unit pipe 18b and branched at the other end to be connected to the second pipe connecting part 26b of each indoor unit 6. A pipe 34 is provided. The first bypass pipe 34 measures a flow control valve 36 as a second flow control unit for controlling the flow rate of the refrigerant flowing through the first bypass pipe 34 and the pressure before and after the flow control valve 36. A first pressure measurement unit 71 and a second pressure measurement unit 72 are provided.

  The relay unit 8 also has three connection ports 84a, 84b, and 84c, and the three-way switching valves 22P to 22R that are the second switching units are connected to either the second connection end 20b or the third connection end 20c. A three-way switching valve 81 is provided as a third switching portion for selectively connecting to either of them.

  Each indoor unit 6 includes a heat exchanger 28 as an indoor heat exchanger and a flow rate control valve 32 (32P, 32Q, 32R) as a first flow rate control unit, and these are the first and second pipes. The connecting portions 26a and 26b are arranged to be in fluid communication. In particular, one end 28a of the heat exchanger 28 is connected to the first pipe connection part 26a via a pipe, and the other end 28b is connected to the second pipe connection part 26b via a pipe 30 to form a second The pipe connection part 26 b is connected to the first bypass pipe 34 of the relay part 8. A flow control valve 32 (32P, 32Q, 32R) for controlling the flow rate of the refrigerant flowing through the pipe 30 is provided in the middle of the pipe 30 of each indoor unit 6P, 6Q, 6R.

Each indoor unit 6 is also provided with a superheat degree measuring unit 73 (73P, 73Q, 73R) that measures the superheat degree of the refrigerant in a pipe connected to one end 28a of the heat exchanger 28.
Each indoor unit 6 is also provided with a temperature measuring unit 90 (90P, 90Q, 90R) that measures the temperature of the refrigerant in a pipe 30 connected to one end 28b of the heat exchanger 28.

  Next, the operation of the air conditioner 2 configured as described above will be described for each operation mode with reference to FIGS. 2 to 9. 2 is a refrigerant circuit diagram showing a refrigerant circulation state in the cooling operation mode of the air-conditioning apparatus according to Embodiment 1 of the present invention, and FIG. 3 is a refrigerant in the heating operation mode of the air-conditioning apparatus according to Embodiment 1 of the present invention. Fig. 4 is a refrigerant circuit diagram showing a circulation state, Fig. 4 is a refrigerant circuit diagram showing a refrigerant circulation state in the cooling main operation mode of the air-conditioning apparatus according to Embodiment 1 of the present invention, and Fig. 5 is based on Embodiment 1 of the present invention. It is a refrigerant circuit figure which shows the refrigerant | coolant circulation state in the heating main operation mode of an air conditioning apparatus. FIG. 6 is a ph diagram (diagram showing the relationship between refrigerant pressure and enthalpy) showing the transition of refrigerant circulation in the cooling operation mode of the air-conditioning apparatus according to Embodiment 1 of the present invention, and FIG. FIG. 8 is a ph diagram showing the transition of refrigerant circulation in the heating operation mode of the air-conditioning apparatus according to Embodiment 1 of the invention, and FIG. 8 is the refrigerant in the cooling-main operation mode of the air-conditioning apparatus according to Embodiment 1 of the present invention. FIG. 9 is a ph diagram showing the transition of refrigerant circulation in the heating main operation mode of the air-conditioning apparatus according to Embodiment 1 of the present invention. In FIGS. 2 to 5, the thick line indicates the piping in which the refrigerant has moved during operation, and the numbers [i] (i = 1, 2,...) In parentheses are p in FIGS. The piping part corresponding to i point (each state of a refrigerant | coolant) on a -h diagram is shown.

[Cooling operation mode] (FIGS. 2 and 6)
When all the indoor units 6P to 6R perform the cooling operation, the first switching unit 16 is in the first flow state (the refrigerant discharge port 10a of the compressor 10 is connected to the one end 12a of the heat exchanger 12, and the refrigerant suction The state in which the port 10b is connected to the first connection end 20a), the opening degree of the flow control valve 36 is fully opened, and the opening degree of the flow control valves 32P to 32R is measured by the superheat degree measurement parts 73P to 73R. The opening degree is controlled in accordance with the degree of superheat of the refrigerant. Moreover, the connection port 24b of each three-way switching valve 22P-22R is closed, and connection port 24a, 24c is open | released. Further, the connection port 84a of the three-way switching valve 81 is closed, and the connection ports 84b and 84c are opened. In this state, the operation of the compressor 10 is started.

First, low-temperature and low-pressure refrigerant vapor is compressed by the compressor 10 and discharged as high-temperature and high-pressure refrigerant. The compression of the refrigerant in the compressor 10 is represented by an isentropic line (point [1] -point [2]) in the ph diagram shown in FIG. 6 assuming that heat does not enter and exit from the surroundings. .
The high-temperature and high-pressure refrigerant discharged from the compressor 10 passes through the first switching unit 16, and the temperature decreases while heating air or the like with the heat exchanger 12. The change of the refrigerant in the heat exchanger 12 is performed under a substantially constant pressure. In consideration of the pressure loss of the heat exchanger 12, a line close to a slightly inclined horizontal line (dots) in the ph diagram. [2] -point [3]). Carbon dioxide as a refrigerant, unlike fluorocarbon refrigerants, is in a supercritical state at high pressure, and thus heats air while the temperature is lowered without condensing.

  The high-pressure refrigerant discharged from the heat exchanger 12 branches through the second connection end 20b, the second inter-unit pipe 18b, and the first bypass pipe 34, and flows into the indoor units 6P to 6R. And the refrigerant | coolant which flowed into each indoor unit 6P-6R is restrict | squeezed by the flow control valves 32P-32R, is expanded (decompressed), and becomes a low-temperature low-pressure gas-liquid two phase state. The change of the refrigerant in the flow control valves 32P to 32R is performed under a constant enthalpy and is represented by a vertical line (point [3] -point [4]) in the ph diagram.

  The refrigerant in the gas-liquid two-phase state changes to low-temperature and low-pressure refrigerant vapor while cooling air or the like with the heat exchanger 28 of the indoor unit 6. The change of the refrigerant in the heat exchanger 28 is performed under a substantially constant pressure. However, in consideration of the pressure loss of the heat exchanger 28, a line (dot) close to a slightly inclined horizontal line in the ph diagram. [4] -point [1]). The low-temperature and low-pressure refrigerant vapors from the heat exchangers 28 of the indoor units 6P to 6R merge after passing through the three-way switching valves 22P to 22R, respectively, and the first inter-unit pipe 18a, the first connection end 20a, It returns to the compressor 10 through the first switching unit 16.

  In addition, compared with the refrigerant | coolant vapor | steam immediately after having come out from the heat exchanger 28, although the refrigerant | coolant vapor | steam inflowing into the compressor 10 passes through piping, a pressure falls a little, but the same point [1] on a ph diagram It is represented by Similarly, the refrigerant flowing into the flow rate control valves 32P to 32R has a slightly lower pressure because it passes through the piping as compared with the high-pressure refrigerant discharged from the heat exchanger 12, but the same point on the ph diagram [ 3]. The slight decrease in the pressure of the refrigerant caused by passing through such a pipe and the pressure loss in the heat exchangers 12 and 28 described above are the same in the following heating operation mode, cooling main operation mode, and heating main operation mode. The description is omitted except for the case.

[Heating operation mode] (FIGS. 3 and 7)
When all the indoor units 6P to 6R perform the heating operation, the first switching unit 16 is in the second flow state (the refrigerant discharge port 10a of the compressor 10 is connected to the first connection end 20a, and the refrigerant is sucked. The state in which the port 10b is connected to the one end 12a of the heat exchanger 12), the flow control valve 36 is set to a fully open state or nearly full open, and the opening degree of the flow control valves 32P to 32R is set to the temperature measuring units 90P to 90R The opening degree is controlled in accordance with the temperature of the refrigerant measured in step (b). Moreover, the connection port 24b of each three-way switching valve 22P-22R is closed, and connection port 24a, 24c is open | released. Further, the connection port 84a of the three-way switching valve 81 is closed, and the connection ports 84b and 84c are opened. In this state, the operation of the compressor 10 is started.

  First, the low-temperature and low-pressure refrigerant vapor (point [1]) is compressed by the compressor 10 and discharged as a high-temperature and high-pressure refrigerant. The high-temperature and high-pressure refrigerant (point [2]) discharged from the compressor 10 passes through the first switching unit 16, passes through the first connection end 20a, and then branches to each of the three-way switching valves 22P to 22R. And flows into the heat exchangers 28 of the indoor units 6P to 6R. The refrigerant heats air or the like with the heat exchanger 28 to lower the temperature (point [3]), and is then squeezed and depressurized with the flow control valves 32P to 32R, respectively, to a low-temperature and low-pressure gas-liquid two-phase state. Change (point [4]). Thereafter, the refrigerant that has come out of each of the indoor units 6P to 6R merges in the first bypass pipe 34, passes through the flow control valve 36, passes through the second inter-unit pipe 18b, and the second connection end 20b, It flows into the other end 12b of the heat exchanger 12. The refrigerant in the gas-liquid two-phase state is cooled to low-temperature and low-pressure refrigerant vapor by cooling air or the like with the heat exchanger 12 (point [1]). Thereafter, the refrigerant passes through the first switching unit 16 and returns to the compressor 10.

[Cooling operation mode] (FIGS. 4 and 8)
When the indoor units 6Q and 6R perform the cooling operation and the indoor unit 6P performs the heating operation, the first switching unit 16 is connected to the first flow state (the refrigerant discharge port 10a of the compressor 10 is connected to the one end 12a of the heat exchanger 12). And a state in which the refrigerant suction port 10b is connected to the first connection end 20a), and the opening degree of the flow rate control valves 32Q and 32R is changed to the superheat degree of the refrigerant measured by the superheat degree measurement parts 73Q and 73R. Accordingly, the opening degree is controlled, and the opening degree of the flow rate control valve 32P is controlled according to the temperature of the refrigerant measured by the temperature measuring unit 90P. Further, the connection port 24b is closed and the connection ports 24a and 24c are opened with respect to the three-way switching valves 22Q and 22R. With respect to the three-way switching valve 22P, the connection port 24a is closed and the connection ports 24b and 24c are opened. Further, the connection port 84b of the three-way switching valve 81 is closed, and the connection ports 84a and 84c are opened.

  The flow control valve 36 controls the opening degree according to the refrigerant pressure measured by the first and second pressure measuring units 71 and 72. For example, the flow control valve 36 is controlled so that the pressure difference at the flow control valve 36 measured by the first and second pressure measuring units 71 and 72 is equal to or less than a predetermined value. In this state, the operation of the compressor 10 is started.

  First, the low-temperature and low-pressure refrigerant vapor (point [1]) is compressed by the compressor 10 and discharged as a high-temperature and high-pressure refrigerant. A part of the high-temperature and high-pressure refrigerant (point [2]) discharged from the compressor 10 passes through the connection end 20c, the third inter-unit piping 18c, the three-way switching valve 81, and the three-way switching valve 22P and enters the indoor unit 6P. Inflow. Then, the temperature of the refrigerant decreases while heating air or the like with the heat exchanger 28 (point [3]), and flows into the first bypass pipe 34 through the flow control valve 32P.

  On the other hand, the remaining high-temperature and high-pressure refrigerant (point [2]) discharged from the compressor 10 passes through the first switching unit 16 and decreases in temperature while heating air or the like in the heat exchanger 12 (point 4). . The high-pressure refrigerant discharged from the heat exchanger 12 passes through the second connection end 20b, the second inter-unit pipe 18b, and the first bypass pipe 34, and the pressure slightly decreases (point 5). It merges with the refrigerant flowing in from 6P (point 6). The merged refrigerant branches and flows into the indoor units 6Q and 6R, is throttled (expanded) by the flow rate control valves 32Q and 32R, and becomes a low-temperature and low-pressure gas-liquid two-phase state (point 7).

  The refrigerant in the gas-liquid two-phase state changes to low-temperature and low-pressure refrigerant vapor while cooling the air or the like with the heat exchanger 28 of the indoor units 6Q and 6R (point 1). The low-temperature and low-pressure refrigerant vapors coming out of the heat exchangers 28 of the indoor units 6Q and 6R merge after passing through the three-way switching valves 22Q and 22R, and the first inter-unit pipe 18a, the first connection end 20a, and the first And return to the compressor 10 through the switching unit 16.

[Heating main operation mode] (FIGS. 5 and 9)
When the indoor units 6P and 6Q perform the heating operation and the indoor unit 6R performs the cooling operation, the first switching unit 16 is in the second flow state (the refrigerant discharge port 10a of the compressor 10 is connected to the first connection end 20a). And the refrigerant inlet 10b is connected to one end 12a of the heat exchanger 12), and the opening degree of the flow rate control valve 32R is opened according to the degree of superheat of the refrigerant measured by the superheat degree measuring unit 73R. The degree of opening is controlled, and the degree of opening of the flow rate control valves 32P and 32Q is controlled according to the temperature of the refrigerant measured by the temperature measuring units 90P and 90Q. Further, the connection ports 24b are closed and the connection ports 24a and 24c are opened with respect to the three-way switching valves 22P and 22Q. With respect to the three-way switching valve 22R, the connection port 24a is closed and the connection ports 24b and 24c are opened. Further, the connection port 84a of the three-way switching valve 81 is closed, and the connection ports 84b and 84c are opened.

  The flow control valve 36 controls the opening degree according to the refrigerant pressure measured by the first and second pressure measuring units 71 and 72. For example, the flow control valve 36 is controlled so that the pressure difference at the flow control valve 36 measured by the first and second pressure measuring units 71 and 72 is equal to or less than a predetermined value. In this state, the operation of the compressor 10 is started.

  First, the low-temperature and low-pressure refrigerant vapor (point [1]) is compressed by the compressor 10 and discharged as a high-temperature and high-pressure refrigerant. The high-temperature and high-pressure refrigerant (point [2]) discharged from the compressor 10 passes through the first switching unit 16, passes through the first connection end 20a, and the first inter-unit pipe 18a, and then branches. Then, it passes through the three-way switching valves 22P and 22Q and flows into the heat exchangers 28 of the indoor units 6P and 6Q. The temperature of the refrigerant is reduced by heating air or the like with the heat exchanger 28 (point [3]). A part of the refrigerant whose temperature has decreased passes through the first bypass pipe 34 and flows into the indoor unit 6R. The refrigerant is throttled and depressurized by the flow control valve 32R, and changed into a low-temperature and low-pressure refrigerant in a gas-liquid two-phase state. (Point [4]), while cooling the air or the like with the heat exchanger 28 of the indoor unit 6R, changes to low-temperature and low-pressure refrigerant vapor (Point 5). Then, it passes through the three-way switching valve 22R and the three-way switching valve 81 and flows into the second inter-unit pipe 18b.

On the other hand, the remaining refrigerant flowing through the first bypass pipe 34 passes through the flow control valve 36 and the pressure is slightly reduced (point [6]), and merges with the refrigerant flowing out from the indoor unit 6R (point [7] ]), The second inter-unit pipe 18b and the second connection end 20b are passed into the other end 12b of the heat exchanger 12, and the air is cooled by the heat exchanger 12 to form low-temperature and low-pressure refrigerant vapor. Change (point [1]). Thereafter, the refrigerant passes through the first switching unit 16 and returns to the compressor 10.

  Thus, according to this air conditioner 2, since only a small amount of the high-temperature and high-pressure refrigerant necessary for heating in the cooling main operation flows through the third inter-unit pipe 18c, the diameter can be reduced. As a result, maintenance and piping installation work are not overly large, and piping parts such as valves and strainers necessary for normal operation can be miniaturized. Further, when the inter-unit piping is long because the installation place between the outdoor unit 4 and the indoor unit 6 is far away, the above problem is more remarkable.

  Also, the refrigerant outlet temperatures of the indoor units 6P to 6R are measured by the temperature measuring units 90P to 90R, and when the refrigerant outlet temperature of the indoor units 6P to 6R rises, the opening degree of the flow control valves 32P to 32 is reduced. Thus, the operating pressure in the indoor units 6P to 6R can be increased to increase the temperature difference between the air and the refrigerant. Conversely, when the outlet temperature of the refrigerant in the indoor units 6P to 6R decreases, the flow control valves 32P to 32 Since the operating pressure in the indoor units 6P to 6R can be reduced to reduce the temperature difference between the air and the refrigerant, an efficient operation can be performed while maintaining the cooling / heating capacity of the indoor units 6P to 6R. it can.

  Moreover, when the superheat degree of the refrigerant | coolant exit of indoor unit 6P-6R is measured by the superheat degree measurement parts 73P-73R and the superheat degree of the refrigerant | coolant exit of indoor unit 6P-6R falls, flow control valve 32P-32R. The degree of superheat at the refrigerant outlet of the indoor units 6P to 6R is increased by narrowing the opening of Conversely, when the degree of superheat at the refrigerant outlet of the indoor units 6P to 6R increases, the degree of superheat at the refrigerant outlet of the indoor units 6P to 6R is reduced by opening the flow control valves 32P to 32R. As a result, the degree of superheat at the outlet of the refrigerant can be kept constant, and the region where the heat transfer performance is poor due to the flow of superheated steam in the indoor heat exchanger can be minimized, so that efficient operation can be performed.

  Further, the opening degree of the flow rate control valve 36 is controlled so that the pressure difference before and after the flow rate control valve 36 measured by the pressure measuring units 71 and 72 becomes a predetermined value or less. Thereby, in the cooling main operation, it is possible to suppress an increase in refrigerant noise and piping vibration in the indoor unit that performs heating. Furthermore, in the heating-main operation, the amount of refrigerant sent to the indoor unit that performs cooling can be controlled, an increase in the pressure loss of the refrigerant can be suppressed, and an efficient operation can be performed.

Embodiment 2. FIG.
FIG. 10 is a refrigerant circuit diagram showing an air-conditioning apparatus according to Embodiment 2 of the present invention. 10, the air conditioner 2A includes an outdoor unit 4A, a plurality of indoor units 6, and a relay unit 8A that connects the outdoor unit 4A and the indoor unit 6 with a refrigerant whose main component is carbon dioxide. A cooling operation mode for cooling all the rooms in which the units 6P to 6R are arranged, a heating operation mode for heating all the rooms, and two modes for cooling one room and heating another room (cooling main operation mode) And heating main operation mode).

The outdoor unit 4A includes a flow path switching unit 52. The flow path switching unit 52 connects the first switching unit 16 and the first connection end 20a in the middle of the pipe 14d, and the other end 12b of the heat exchanger 12 and the second connection end 20b. Check valves 54 and 56 are provided in the middle of the pipe 14e to be connected. The check valve 54 allows the refrigerant to flow only from the first connection end 20 a to the first switching unit 16. On the other hand, the check valve 56 allows the refrigerant to flow only from the heat exchanger 12 to the second connection end 20b.

  Further, the flow path switching unit 52 has one end at the site of the pipe 14d between the first switching unit 16 and the check valve 54, and the other end between the check valve 56 and the second connection end 20b. A bypass pipe 58 connected to the midpoint of the pipe 14e is provided. In the middle of the bypass pipe 58, a check valve 60 that allows the refrigerant to flow only from the first switching unit 16 to the second connection end 20b is provided. The flow path switching unit 52 further has one end at the midpoint of the pipe 14d between the first connection end 20a and the check valve 54, and the other end at the pipe between the check valve 56 and the heat exchanger 12. The bypass piping 62 connected to the site | part 14e is provided. In the middle of the bypass pipe 62, a check valve 64 that allows the refrigerant to flow only from the first connection end 20a to the heat exchanger 12 is provided.

  The relay portion 8A has a second bypass pipe 82 having one end connected to the first bypass pipe 34 and the other end connected to the first inter-unit pipe 18a, and the flow rate of the refrigerant flowing through the second bypass pipe 82. A third pressure measuring unit 74 that measures the pressure before and after the flow rate control valve 83 is provided together with a flow rate control valve 83 and a second pressure control unit 72 as a third flow rate control unit for controlling the flow rate. Since other configurations are the same as those in the first embodiment, description thereof is omitted.

  Next, the operation of the air conditioner 2A configured as described above will be described for each operation mode with reference to FIGS. 11 is a refrigerant circuit diagram showing a refrigerant circulation state in the cooling operation mode of the air-conditioning apparatus according to Embodiment 2 of the present invention, and FIG. 12 is a refrigerant in the heating operation mode of the air-conditioning apparatus according to Embodiment 2 of the present invention. Fig. 13 is a refrigerant circuit diagram showing a circulation state, Fig. 13 is a refrigerant circuit diagram showing a refrigerant circulation state in the cooling main operation mode of the air-conditioning apparatus according to Embodiment 2 of the present invention, and Fig. 14 is based on Embodiment 2 of the present invention. It is a refrigerant circuit figure which shows the refrigerant | coolant circulation state in the heating main operation mode of an air conditioning apparatus.

[Cooling operation mode] (Fig. 11)
When all the indoor units 6P to 6R perform the cooling operation, the first switching unit 16 is in the first flow state (the refrigerant discharge port 10a of the compressor 10 is connected to the one end 12a of the heat exchanger 12, and the refrigerant suction The state in which the port 10b is connected to the first connection end 20a), the opening degree of the flow control valve 36 is fully opened, and the flow control valves 32P to 32R are made of the refrigerant measured by the superheat degree measurement units 73P to 73R. The opening degree is controlled according to the degree of superheat. Further, the flow control valve 83 is fully closed, the connection ports 24b of the three-way switching valves 22P to 22R are closed, and the connection ports 24a and 24c are opened. Further, the connection port 84a of the three-way switching valve 81 is closed, and the connection ports 84b and 84c are opened. In this state, the operation of the compressor 10 is started.

  First, low-temperature and low-pressure refrigerant vapor is compressed by the compressor 10 and discharged as high-temperature and high-pressure refrigerant. The high-temperature and high-pressure refrigerant discharged from the compressor 10 passes through the first switching unit 16, and the temperature decreases while heating air or the like with the heat exchanger 12.

  The high-pressure refrigerant discharged from the heat exchanger 12 flows into the flow path switching unit 52 and passes through the check valve 56, the second connection end 20b, the second inter-unit pipe 18b, and the first bypass pipe 34. Then, it branches and flows into the indoor units 6P to 6R, is throttled by the flow control valves 32P to 32R, is expanded (decompressed), and becomes a low-temperature low-pressure gas-liquid two-phase state.

  The refrigerant in the gas-liquid two-phase state changes to low-temperature and low-pressure refrigerant vapor while cooling air or the like with the heat exchanger 28 of the indoor unit 6. The low-temperature and low-pressure refrigerant vapors coming out of the heat exchangers 28 of the indoor units 6P to 6R merge after passing through the three-way switching valves 22P to 22R, and pass through the first inter-unit pipe 18a and the first connection end 20a. As described above, the refrigerant flows into the flow path switching unit 52 and returns to the compressor 10 through the check valve 54 and the first switching unit 16.

[Heating operation mode] (Fig. 12)
When all the indoor units 6P to 6R perform the heating operation, the first switching unit 16 is in the second flow state (the refrigerant discharge port 10a of the compressor 10 is connected to the first connection end 20a, and the refrigerant is sucked. The state in which the port 10b is connected to the one end 12a of the heat exchanger 12), the flow rate control valve 36 is set to be fully closed, and the opening degree of the flow rate control valves 32P to 32R is measured by the temperature measuring units 90P to 90R. The opening degree is controlled according to the temperature of the refrigerant. Further, the flow control valve 83 is fully opened, the connection ports 24a of the three-way switching valves 22P to 22R are closed, and the connection ports 24b and 24c are opened. Further, the connection port 84a of the three-way switching valve 81 is closed, and the connection ports 84b and 84c are opened. In this state, the operation of the compressor 10 is started.

  First, low-temperature and low-pressure refrigerant vapor is compressed by the compressor 10 and discharged as high-temperature and high-pressure refrigerant. The high-temperature and high-pressure refrigerant discharged from the compressor 10 passes through the first switching unit 16, flows into the flow path switching unit 52, passes through the bypass pipe 58, passes through the check valve 60, the second connection end 20 b, After passing through the second inter-unit pipe 18b and the three-way switching valve 81, it branches and passes through the three-way switching valves 22P to 22R and flows into the heat exchangers 28 of the indoor units 6P to 6R. The refrigerant heats air or the like with the heat exchanger 28 to lower the temperature, and is then squeezed and depressurized by the flow control valves 32P to 32R to change into a low-temperature and low-pressure gas-liquid two-phase state. Thereafter, the refrigerant that has exited from the indoor units 6P to 6R merges in the first bypass pipe 34 and flows into the second bypass pipe 82. The refrigerant flowing into the second bypass pipe 82 flows into the flow path switching unit 52 through the flow control valve 83, through the first inter-unit pipe 18a, and the first connection end 20a, and into the bypass pipe 62, It passes through the check valve 64 and flows into the other end 12 b of the heat exchanger 12. The refrigerant in the gas-liquid two-phase state is cooled to air or the like by the heat exchanger 12 and changed to low-temperature and low-pressure refrigerant vapor. Thereafter, the refrigerant passes through the first switching unit 16 and returns to the compressor 10.

[Cooling operation mode] (Fig. 13)
When the indoor units 6Q and 6R perform the cooling operation and the indoor unit 6P performs the heating operation, the first switching unit 16 is connected to the first flow state (the refrigerant discharge port 10a of the compressor 10 is connected to the one end 12a of the heat exchanger 12). And a state in which the refrigerant suction port 10b is connected to the first connection end 20a), and the opening degree of the flow rate control valves 32Q and 32R is changed to the superheat degree of the refrigerant measured by the superheat degree measurement parts 73Q and 73R. Accordingly, the opening degree is controlled, and the opening degree of the flow rate control valve 32P is controlled according to the temperature of the refrigerant measured by the temperature measuring unit 90P. Further, the connection port 24b is closed with respect to the three-way switching valves 22Q and 22R, and the connection ports 24a and 24c are opened. With respect to the three-way switching valve 22P, the connection port 24a is closed and the connection ports 24b and 24c are opened. Further, the connection port 84b of the three-way switching valve 81 is closed, and the connection ports 84a and 84c are opened.

  The flow control valve 83 is fully closed, and the flow control valve 36 controls the opening degree according to the refrigerant pressure measured by the first and second pressure measuring units 71 and 72. For example, the flow control valve 36 is controlled so that the pressure difference at the flow control valve 36 measured by the first and second pressure measuring units 71 and 72 is equal to or less than a predetermined value. In this state, the operation of the compressor 10 is started.

  First, the low-temperature and low-pressure refrigerant vapor is compressed by the compressor 10 and discharged as a high-temperature and high-pressure refrigerant. A part of the high-temperature and high-pressure refrigerant discharged from the compressor 10 flows into the indoor unit 6P through the connection end 20c, the third inter-unit pipe 18c, the three-way switching valve 81, and the three-way switching valve 22P, and is then supplied to the heat exchanger. The temperature is lowered while heating air or the like at 28, and flows into the first bypass pipe 34 through the flow control valve 32P.

  On the other hand, the remaining high-temperature and high-pressure refrigerant discharged from the compressor 10 passes through the first switching unit 16 and decreases in temperature while heating the air or the like in the heat exchanger 12. The high-pressure refrigerant discharged from the heat exchanger 12 flows into the flow path switching unit 52 and passes through the check valve 56, the second connection end 20b, the second inter-unit pipe 18b, and the first bypass pipe 34. The pressure drops slightly and merges with the refrigerant that has flowed out of the indoor unit 6P. Then, the merged refrigerant branches and flows into the indoor units 6Q and 6R, is throttled (expanded) by the flow control valves 32Q and 32R, and becomes a low-temperature and low-pressure gas-liquid two-phase state.

  The refrigerant in the gas-liquid two-phase state changes to low-temperature and low-pressure refrigerant vapor while cooling air or the like with the heat exchanger 28 of the indoor units 6Q and 6R. The low-temperature and low-pressure refrigerant vapors coming out of the heat exchangers 28 of the indoor units 6Q and 6R merge after passing through the three-way switching valves 22Q and 22R, and the first inter-unit pipe 18a, the first connection end 20a, and the first And return to the compressor 10 through the switching unit 16.

[Heating main operation mode] (Fig. 14)
When the indoor units 6P and 6Q perform the heating operation and the indoor unit 6R performs the cooling operation, the first switching unit 16 is in the second flow state (the refrigerant discharge port 10a of the compressor 10 is connected to the first connection end 20a). And the refrigerant inlet 10b is connected to one end 12a of the heat exchanger 12), and the opening degree of the flow rate control valve 32R is opened according to the degree of superheat of the refrigerant measured by the superheat degree measuring unit 73R. The degree of opening is controlled, and the degree of opening of the flow rate control valves 32P and 32Q is controlled according to the temperature of the refrigerant measured by the temperature measuring units 90P and 90Q. Further, the connection port 24a is closed and the connection ports 24b and 24c are opened with respect to the three-way switching valves 22P and 22Q. With respect to the three-way switching valve 22R, the connection port 24b is closed and the connection ports 24a and 24c are opened. Further, the connection port 84a of the three-way switching valve 81 is closed, and the connection ports 84b and 84c are opened.

  Further, the flow control valve 36 is fully closed, and the flow control valve 83 controls the opening according to the refrigerant pressure measured by the second and third pressure measuring units 72 and 74. For example, the flow control valve 83 is controlled so that the pressure difference at the flow control valve 83 measured by the second and third pressure measuring units 72 and 74 is equal to or less than a predetermined value. In this state, the operation of the compressor 10 is started.

  First, low-temperature and low-pressure refrigerant vapor is compressed by the compressor 10 and discharged as high-temperature and high-pressure refrigerant. The high-temperature and high-pressure refrigerant discharged from the compressor 10 passes through the first switching unit 16 and flows into the bypass pipe 58 of the flow path switching unit 52, and the check valve 60, the first connection end 20 b, the second After passing through the inter-unit pipe 18b, it branches, passes through the three-way switching valves 22P, 22Q, and flows into the heat exchangers 28 of the indoor units 6P, 6Q. The temperature of the refrigerant decreases as the air is heated by the heat exchanger 28. A part of the refrigerant whose temperature has decreased passes through the first bypass pipe 34, flows into the indoor unit 6R, is throttled by the flow control valve 32R, and is reduced in pressure to change into a low-temperature and low-pressure gas-liquid two-phase refrigerant. While the air is cooled by the heat exchanger 28 of the indoor unit 6R, the refrigerant changes to low-temperature and low-pressure refrigerant vapor. Then, it flows into the second inter-unit pipe 18a through the three-way switching valve 22R.

  On the other hand, the remaining refrigerant flowing through the first bypass pipe 34 flows into the second bypass pipe 82, and the pressure is slightly lowered through the flow rate control valve 83, and merges with the refrigerant that has flowed out of the indoor unit 6R. The merged refrigerant passes through the first inter-unit pipe 18a and the first connection end 20a, flows into the bypass pipe 62 of the flow path switching unit 52, passes through the check valve 64, and passes through the check valve 64. It flows into the other end 12b, cools air etc. with the heat exchanger 12, and changes into low-temperature and low-pressure refrigerant vapor. Thereafter, the refrigerant passes through the first switching unit 16 and returns to the compressor 10.

Thus, according to this air conditioning apparatus 2A, an effect equivalent to the effect of Embodiment 1 can be obtained.
The air conditioner 2A includes a flow path switching unit 52 so that the high-temperature and high-pressure refrigerant compressed by the compressor 10 flows from the second connection end 20b to the second inter-unit pipe 18b. Yes. Therefore, since only the low-pressure refrigerant flows through the first inter-unit pipe 18a, there is an effect that the thickness of the pipe can be reduced.

  In addition, the flow rate switching unit 52 arranges (intervenes) the check valve 54 in the course of the pipe 14d connecting the first switching unit 16 and the first connection end 20a, and heats the check valve 56. The other end 12b of the exchanger 12 and the second connection end 20b are disposed in the middle of the path of the pipe 14e, and the check valve 64 is connected to the other end 12b of the heat exchanger 12 and the first connection end 20a. Is arranged in the middle of the path of the bypass pipe 62 that connects the first switching unit 16 and the second connection end 20b, and is arranged in the middle of the path of the bypass pipe 58 that connects the first switching unit 16 and the second connection end 20b. Since it is comprised, the flow-path switching part 52 is realizable with a simple structure.

In the cooling main operation, the opening degree of the flow rate control valve 36 is controlled so that the pressure difference before and after the flow rate control valve 36 measured by the pressure measuring units 71 and 72 is equal to or less than a predetermined value. Thereby, increase of the refrigerant | coolant sound and piping vibration in an indoor unit can be suppressed by the cooling main operation.
In the heating main operation, the opening degree of the flow control valve 83 is controlled such that the pressure difference before and after the flow control valve 83 measured by the pressure measuring units 71 and 72 is equal to or less than a predetermined value. As a result, the amount of refrigerant sent to the indoor unit that performs cooling in the heating-main operation can be controlled, an increase in the pressure loss of the refrigerant can be suppressed, and an efficient operation can be performed.

Embodiment 3 FIG.
In this Embodiment 3, it replaces with each three-way switching valve 22P-22R, and the said Embodiment 1, except the point provided with the same number of pairs of 1st and 2nd two-way switching valves as the indoor unit 6. It is comprised similarly to 2.
That is, the first inter-unit pipe 18a has one end connected to the first connection end 20a, the other end branched, and connected to one connection port of each pair of first two-way switching valves. Yes. The second inter-unit pipe 18b has one end connected to the second connection end 20b and the other end branched to be connected to one connection port of each pair of second two-way switching valves. Yes. And the other connection port of the 1st and 2nd two-way selector valve is connected to the 1st piping connection part 26a of the corresponding indoor unit 6 via piping.

  According to the third embodiment, since the flow of the refrigerant flowing through the first and second two-way switching valve is always constant, there is no need to use a valve corresponding to the bidirectional flow, and the second switching The part can be realized with a valve having a simple structure.

  Here, in the third embodiment, a case where two two-way switching valves are used for one three-way switching valve 22 constituting the second switching unit in the first and second embodiments will be described. However, the one three-way switching valve 81 constituting the third switching unit in the first and second embodiments may be constituted by two two-way switching valves.

  In each of the above embodiments, carbon dioxide alone is used as the refrigerant. However, a refrigerant mainly composed of carbon dioxide, a fluorocarbon refrigerant, or a hydrocarbon refrigerant may be used. Further, if carbon dioxide or a refrigerant mainly composed of carbon dioxide is used, global warming can be suppressed.

  In each of the above embodiments, the configuration in which the temperature measuring unit 90 is provided at the other end 28b of the heat exchanger 28 has been described. However, when the refrigerant pressure is equal to or lower than the critical pressure, the degree of supercooling of the refrigerant is measured. A possible supercooling degree measurement unit may be provided to control the opening degree of the flow control valve 32 according to the supercooling degree of the refrigerant.

In the above embodiments, the specific configuration of the first switching unit 16 is not described in detail, but the first switching unit 16 can switch the direction of the refrigerant flowing in the outdoor heat exchanger 12. For example, a four-way switching valve can be used.
In each of the above embodiments, the first switching unit and the second switching unit may operate independently.

  In the present invention, the “unit” of the indoor unit and the outdoor unit does not necessarily mean that all the components are provided in the same housing or the outer wall of the housing. For example, even if the flow control valve 32 of the indoor unit is disposed at a location different from the housing in which the indoor heat exchanger 28 is accommodated, such a configuration is included in the scope of the present invention. In addition, multiple sets of outdoor heat exchangers and compressors are provided in the outdoor unit, and the refrigerant flowing out from each set is merged to flow through one inter-unit piping, and the refrigerant from the other inter-unit piping is branched. May be allowed to flow into each set.

It is a refrigerant circuit diagram which shows the air conditioning apparatus which concerns on Embodiment 1 of this invention. It is a refrigerant circuit diagram which shows the refrigerant | coolant circulation state in the air_conditioning | cooling operation mode of the air conditioning apparatus which concerns on Embodiment 1 of this invention. It is a refrigerant circuit diagram which shows the refrigerant | coolant circulation state in the heating operation mode of the air conditioning apparatus which concerns on Embodiment 1 of this invention. It is a refrigerant circuit diagram which shows the refrigerant | coolant circulation state in the air conditioning main body operation mode of the air conditioning apparatus which concerns on Embodiment 1 of this invention. It is a refrigerant circuit diagram which shows the refrigerant | coolant circulation state in the heating main operation mode of the air conditioning apparatus which concerns on Embodiment 1 of this invention. It is a ph diagram which shows the change of the refrigerant circulation in the air conditioning operation mode of the air harmony device concerning Embodiment 1 of this invention. It is a ph diagram which shows the change of the refrigerant circulation in the heating operation mode of the air harmony device concerning Embodiment 1 of this invention. It is a ph diagram which shows the change of the refrigerant circulation in the cooling main operation mode of the air harmony device concerning Embodiment 1 of this invention. It is a ph diagram which shows the change of the refrigerant circulation in the heating main operation mode of the air harmony device concerning Embodiment 1 of this invention. It is a refrigerant circuit figure which shows the air conditioning apparatus which concerns on Embodiment 2 of this invention. It is a refrigerant circuit figure which shows the refrigerant | coolant circulation state in the air_conditioning | cooling operation mode of the air conditioning apparatus which concerns on Embodiment 2 of this invention. It is a refrigerant circuit figure which shows the refrigerant | coolant circulation state in the heating operation mode of the air conditioning apparatus which concerns on Embodiment 2 of this invention. It is a refrigerant circuit figure which shows the refrigerant | coolant circulation state in the air conditioning main body operation mode of the air conditioning apparatus which concerns on Embodiment 2 of this invention. It is a refrigerant circuit figure which shows the refrigerant | coolant circulation state in the heating main operation mode of the air conditioning apparatus which concerns on Embodiment 2 of this invention.

Explanation of symbols

  4, 4A outdoor unit, 6P to 6R indoor unit, 8, 8A relay unit, 10 compressor, 10a refrigerant outlet, 10b refrigerant inlet, 12 heat exchanger (outdoor heat exchanger), 16 first switching unit, 18a 1st inter-unit piping, 18b 2nd inter-unit piping, 18c 3rd inter-unit piping, 20a 1st connection end, 20b 2nd connection end, 20c 3rd connection end, 22P- 22R three-way switching valve (second switching portion), 26a first piping connection portion, 26b second piping connection portion, 28 heat exchanger (indoor heat exchanger), 32P to 32R flow control valve (first flow rate) Control unit), 34 first bypass piping, 36 flow control valve (second flow control unit), 52 flow path switching unit, 54, 56, 60, 64 check valve, 71 first pressure measurement unit, 72 2nd pressure measurement part, 73P-73 Superheat measurement unit, 74 third pressure measurement unit, 81 three-way switching valve (third switching unit), 82 second bypass piping, 83 flow control valve (third flow control unit), 90P-90R temperature measurement Department.

Claims (7)

An outdoor heat exchanger disposed to fluidly communicate between the first and second connection ends, a compressor that compresses and discharges the refrigerant, and a first that switches the direction of the refrigerant flowing through the outdoor heat exchanger. And an outdoor unit having a third connection end connected to the discharge side of the compressor,
A plurality of indoor heat exchangers arranged to fluidly communicate between the first and second pipe connecting portions and a first flow rate control unit for controlling the flow rate of refrigerant flowing through the indoor heat exchanger. With indoor units
A plurality of second switching parts for selectively connecting each of the first pipe connection parts of each of the plurality of indoor units to one of the first and second connection end parts, one end of which is the first A first inter-unit pipe connected to each of the plurality of second switching units, one end connected to the second connection end, and the other. A second inter-unit pipe connected to each of the plurality of second switching sections with an end branched, one end connected to the third connection end, and the other end connected to the second inter-unit pipe The third inter-unit pipe connected, the second inter-unit pipe and the third inter-unit pipe are connected to each other, and the second switching part is connected to the second and third connection ends. A third switching portion for selectively connecting to either one of the first and second ends; A first bypass connected to the second connection end of the third switching portion of the inter-pipe and having the other end branched and connected to the second pipe connection of each of the plurality of indoor units A relay part having a second flow rate control part for controlling the flow rate of the refrigerant flowing through the pipe and the first bypass pipe;
An air conditioner comprising:   The air conditioner according to claim 1, wherein carbon dioxide or a refrigerant mainly composed of carbon dioxide is used. The compressor has a refrigerant suction port and a refrigerant discharge port,
The first switching unit connects the refrigerant discharge port to one end of the outdoor heat exchanger and connects the refrigerant suction port to the first connection end according to an operation mode. Switching between a state and two flow states in which the refrigerant discharge port is connected to the first connection end and the refrigerant suction port is connected to the one end of the outdoor heat exchanger;
When the first switching unit is in the first flow state, the refrigerant from the other end of the outdoor heat exchanger is guided to the second connection end, and from the first connection end. When the first switching unit is in the second flow state, the refrigerant from the refrigerant discharge port of the compressor is connected to the second connection when the refrigerant is guided to the refrigerant suction port of the compressor. A flow path switching unit that guides the refrigerant from the first connection end to the other end of the outdoor heat exchanger, one end connected to the first bypass pipe, and the other end 2. The second bypass pipe connected to the first inter-unit pipe, and a third flow rate control unit for controlling the flow rate of the refrigerant flowing through the second bypass pipe. Air conditioner.   The flow path switching unit includes a first check valve interposed in a first flow path between the first connection end and the compressor, the second connection end, and the outdoor heat exchange. A second check valve interposed in a second flow path between the first and the third flow path, and a third reverse valve interposed in a third flow path between the first connection end and the outdoor heat exchanger. The air conditioner according to claim 3, further comprising: a stop valve; and a fourth check valve interposed in a fourth flow path between the second connection end and the compressor. .   Each of the second switching units includes a first two-way switching valve connected to the branched other end of the first inter-unit piping and the first piping connection of the corresponding indoor unit; 2. The second two-way switching valve connected to the other branched end of the second inter-unit piping and the first piping connection portion of the corresponding indoor unit. Air conditioner.   The second flow rate control unit or the third flow rate control unit controls the opening degree according to the state of the refrigerant at the inlet / outlet of the second flow rate control unit or the third flow rate control unit or the state of the refrigerant at the outlet, respectively. The air conditioner according to claim 1 or 3, wherein the air conditioner is provided.   The air conditioner according to claim 1, wherein the first flow rate control unit is controlled according to a state of a refrigerant at an outlet of the indoor heat exchanger of the indoor unit corresponding to the opening degree.

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