JP2002340390A - Air conditioner for multiple rooms - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner for multiple rooms, in which refrigerant is prevented from creating a sound due to a pressure difference at a start time of heating operation of an indoor unit by providing a bypass pipe on both ends of an opening/closing valve on the discharge side in a distribution unit, and performing an effective operation without allowing the refrigerant to flow in unoperated indoor units. SOLUTION: In this air conditioner, a cooling operation and a heating operation can be conducted selectively or simultaneously for each indoor unit. A bypass pipe 19 having an opening/closing control valve 20 is connected on both ends of a third opening/closing valve 12 in the distribution unit 2, and pressure detection means for detecting a refrigerant pressure is provided to pipes of each of indoor heat-exchangers 3a, 3b, 3c. When heating operation is started in an indoor unit in operation stop, the third valve 12 and a fourth opening/ closing valve 13 corresponding to the unit are closed and the valve 20 is opened. After predetermined time, an electronic expansion valve 17 on the indoor side is opened, thereafter, when a refrigerant pressure of an heat-exchanger 15 has reached a predetermined pressure, the third opening/closing valve 12 is opened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-room air conditioner in which a plurality of indoor units are connected to one outdoor unit. More specifically, the present invention relates to generation of refrigerant noise generated at the start of heating operation. The present invention relates to a configuration of a refrigerant circuit that can prevent the above and can shorten a heating start time.

[0002]

2. Description of the Related Art Conventional multi-room air conditioners of this type include:
For example, there is one as shown in FIG. In the figure, 1
Is an outdoor unit installed outside the room, 2 is a branching unit installed behind the ceiling in the room, etc., and 3a, 3b and 3c are three indoor units. The outdoor unit 1 mainly includes a compressor 4, an outdoor heat exchanger 5, and an electronic expansion valve 6 on the outdoor side. One of a first pipe (discharge gas pipe) 7 is provided on a discharge side of the compressor 4, One of second pipes (suction gas pipes) 8 is connected to the suction side, and the other is connected to the branch unit, respectively. The first on-off valve 9, the outdoor heat exchanger 5, and the electronics are connected from the discharge side of the compressor 4. The third pipe (liquid pipe) 10 is sequentially connected to one of the third pipes (liquid pipes) 10 via the expansion valve 6, and the other of the third pipe 10 is connected to the flow dividing unit. Also, the second open / close valve 11 is connected between the suction side of the compressor 4 and the space between the first open / close valve 9 and the outdoor heat exchanger 5.
Connected through.

The branch unit 2 mainly includes a branch pipe that branches from the first pipe 7, the second pipe 8, and the third pipe 10 from the outdoor unit 1 to the indoor units 3a, 3b, and 3c. The third on-off valve 12 is provided on the branch pipe of the first pipe 7 and the fourth on-off valve 13 is provided on the branch pipe of the second pipe 8, respectively. Fourth on-off valve
13 are connected in parallel to each other, connected to the respective indoor heat exchangers 15 of the indoor units 3a, 3b, and 3c at a fourth pipe 14, and from a branch pipe of the third pipe 10 to a fifth pipe 16 Each of the indoor units 3a, 3b, 3c is connected to an electronic expansion valve 17 on the indoor side.

The indoor units 3a, 3b, 3c mainly comprise an indoor heat exchanger 14 and an indoor electronic expansion valve 17, and a fourth pipe 14 from the branch unit 2 is connected to the indoor heat exchanger. Fifteen
The other side of the indoor heat exchanger 15 is connected to one side of the indoor-side electronic expansion valve 17, and the indoor-side electronic expansion valve 17
A fifth pipe 16 from the flow dividing unit 2 is connected to the other side.

In the above configuration, the indoor unit 3a is in a heating operation, the indoor unit 3b is in a stopped state, and the indoor unit 3c
The state in which the heating operation is started from the stop will be described.
The second on-off valve 11 and the third on-off valve 12 of the indoor unit 3a
And the first on-off valve 9 and the fourth on-off valve 13 of the indoor unit 3a are closed, so that the high-temperature and high-pressure refrigerant vapor discharged from the compressor 4 is discharged from the first The refrigerant enters the indoor heat exchanger 15 of the indoor unit 3a through the pipe 7, and radiates heat into the room by the indoor heat exchanger 15 to warm the room. Liquid, and expands at the indoor side electronic expansion valve 17 to become a low-temperature and low-pressure refrigerant liquid, enters the outdoor heat exchanger 5 through the third pipe 10, and outputs the outdoor heat at the outdoor heat exchanger 5. And evaporates into low-temperature, low-pressure refrigerant vapor,
The refrigerant is sucked into the compressor 4 through the second on-off valve 11 and is compressed by the compressor 4 to become a high-temperature and high-pressure refrigerant vapor, thereby forming one refrigeration cycle, and the indoor unit 3a is operated for heating.

On the other hand, when the indoor unit 3c is stopped, the indoor electronic expansion valve 17 and the third on-off valve 12 corresponding to the indoor unit 3c are closed, and the fourth on-off valve 13 is open. The indoor heat exchanger 15 side has a low pressure after the third on-off valve 12 in the state. Further, the pressure on the first pipe (discharge gas pipe) 7 side of the third on-off valve 12 is high. When the indoor unit 3c starts the heating operation from this stopped state, the indoor-side electronic expansion valve 17 and the third on-off valve 12 are opened, the fourth on-off valve 13 is closed, and the high-pressure refrigerant on the discharge side of the compressor 4 is dashed arrow As shown by, the third on-off valve 12, the indoor heat exchanger 15, the indoor electronic expansion valve
17, returning to the compressor 4 through the same path as the indoor unit 3a through the third pipe 10, and the indoor unit 3c is operated for heating.

However, in the above configuration, when the heating operation is started, the third on-off valve 12 is opened, and the high-pressure portion and the low-pressure portion are connected at once, so that a loud refrigerant noise due to the pressure difference is generated. Therefore, when all the operation indoor units in the same refrigerant system are performing the heating operation, a small amount of refrigerant is also supplied to the stopped indoor units. However, in the case of an indoor unit installed in a small room or the like, the room is warmed by the heat radiation from the indoor heat exchanger 15 even when the indoor unit is stopped. In addition, there is a problem that a large amount of refrigerant is circulated and the efficiency is reduced.

[0008]

In view of the above problems, in the present invention, bypass pipes are provided at both ends of a discharge-side opening / closing valve in a flow dividing unit, and refrigerant is not supplied to a stopped indoor unit to reduce the efficiency. It is an object of the present invention to provide a multi-room air conditioner that enables good operation and can prevent generation of refrigerant noise caused by a pressure difference when an indoor unit starts a heating operation.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is characterized in that a branch is made from a discharge side of a compressor, and a first open / close valve, an outdoor heat exchanger, an electronic expansion valve, While connecting the connecting portion, connecting the second connecting portion to the other pipeline, connecting the third connecting portion to one of the pipelines to the suction side of the compressor, while connecting the other pipeline and the first An outdoor unit having a second on-off valve connected between the on-off valve and the outdoor heat exchanger, and a first pipe connected to the second connection portion, branched from the first pipe, and a plurality of third on-off valves. While connected in parallel, a second pipe is connected to the third connection portion, branched from the second pipe, a plurality of fourth on-off valves are connected in parallel, and the third on-off valves and the fourth The on-off valves and the on-off valves are respectively connected in parallel, each is connected to a plurality of fourth pipes, and a third pipe is connected to the first connection portion. A branch unit branched from a pipe and a plurality of fifth pipes connected in parallel, and a plurality of indoor units connected to the fifth pipe via an indoor heat exchanger and an indoor-side electronic expansion valve from the fourth pipe. By controlling the opening and closing of the first on-off valve, the second on-off valve, the third on-off valve and the fourth on-off valve according to the operating state, cooling operation and heating operation for each of the plurality of indoor units Selectively, or can be performed simultaneously, in a multi-room air conditioner configured to enable simultaneous cooling and heating operation by stopping the outdoor heat exchanger, At both ends of each of the third on-off valves, a bypass pipe having an on-off control valve is connected, and pressure detecting means for detecting a refrigerant pressure is provided on a pipe of each of the indoor heat exchangers. Heating operation When starting, the third on-off valve and the fourth on-off valve corresponding to the indoor unit are closed, the on-off control valve is opened, and after a lapse of a predetermined time, the indoor-side electronic expansion valve is opened. After the refrigerant pressure in the exchanger reaches a predetermined pressure, the third on-off valve is controlled to be opened.

[0010] A branch from the discharge side of the compressor connects the first on-off valve, the outdoor heat exchanger, the electronic expansion valve, and the first connecting portion to one pipe, and connects the second pipe to the other pipe. Connecting the connecting portion and connecting the third connecting portion to one of the pipelines leading to the suction side of the compressor, and performing the second opening and closing between the other pipeline and the first on-off valve and the outdoor heat exchanger. An outdoor unit to which a valve is connected, a first pipe connected to the second connection part, branched from the first pipe, and a plurality of third on-off valves are connected in parallel, while a second pipe is connected to the third connection part. The pipes are connected, branched from the second pipe, and a plurality of fourth on-off valves are connected in parallel, and the plurality of third on-off valves and the fourth on-off valves are respectively connected in parallel to each other to form a plurality of A fourth pipe is connected, a third pipe is connected to the first connection part, a branch is made from the third pipe, and a plurality of fifth pipes are connected in parallel. And a plurality of indoor units connected to the fifth pipe via an indoor heat exchanger and an indoor-side electronic expansion valve from the fourth pipe, the first on-off valve, the second on-off By controlling the opening and closing of the valve, the third on-off valve and the fourth on-off valve in accordance with the operation state, the cooling operation and the heating operation can be selectively or simultaneously performed for each of the plurality of indoor units, and further, In a multi-room air conditioner configured to enable simultaneous cooling and heating operation by stopping the outdoor heat exchanger,
A bypass pipe having a series circuit of an on-off control valve and a capillary tube is connected to both ends of the third on-off valve in the flow dividing unit, and a refrigerant is connected to each of the indoor heat exchanger piping and the bypass pipe. Providing pressure detecting means for detecting pressure, when starting the heating operation of the indoor unit in a stop, while closing the third on-off valve and the fourth on-off valve corresponding to the indoor unit, open the on-off control valve, After a lapse of a predetermined time, the electronic expansion valve on the indoor side is opened, and thereafter, after the pressure difference between the refrigerant pressure in the indoor heat exchanger and the refrigerant pressure in the bypass pipe reaches a predetermined value, control is performed to open the third on-off valve. It has become.

[0011] Further, a solenoid valve is used as the opening / closing control valve.

Further, an electronic expansion valve is used as the opening / closing control valve.

Further, a pressure sensor or a pressure switch is used as the pressure detecting means.

[0014] Further, the flow dividing unit comprises a plurality of flow dividing units respectively corresponding to the plurality of indoor units and each including a bypass pipe having the third opening / closing valve, the fourth opening / closing valve, and the opening / closing control valve. It has become.

Further, an oil separator is provided on the discharge side of the compressor for separating oil and returning the oil to the suction side of the compressor.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below as examples based on the attached drawings. FIG. 1 is a configuration diagram of a refrigerant circuit in an embodiment of a multi-room air conditioner according to the present invention. In the figure, 1 is an outdoor unit installed outside the room, 2 is a shunt unit installed behind the ceiling in the room, and 3a, 3b, 3c are three indoor units connected in parallel, respectively.

The outdoor unit 1 branches from the discharge side of the compressor 4 and has a first opening / closing valve 9, an outdoor heat exchanger 5, an outdoor electronic expansion valve 6, and a first connection portion A1 in one of its pipelines. On the other hand, the second connecting part A2 is connected to the other pipe line, the branch is branched from the suction side of the compressor 4, the third connecting part A3 is connected to one of the pipe lines, and the other pipe line is connected. A second on-off valve 11 is connected between the first on-off valve 9 and the outdoor heat exchanger 5.

The branch unit 2 is connected to the second connection part A2.
A first pipe (discharge gas pipe) 7 is connected to the first pipe 7 and branched from the first pipe 7 to connect a plurality of third on-off valves 12 in parallel.
A second pipe (intake gas pipe) 8 is connected to the third connection portion A3, branched from the second pipe 8, and a plurality of fourth on-off valves 13 are connected in parallel. 12 and the fourth on-off valve 13 are connected in parallel, respectively, and each is connected to a plurality of fourth pipes.
14, a third pipe (liquid pipe) 10 is connected to the first connection part A1, and a branch is made from the third pipe 10, and a plurality of fifth pipes 16 are connected in parallel.

The indoor units 3a, 3b, 3c are mainly composed of an indoor heat exchanger 15 and an electronic expansion valve 17 on the indoor side, and a fourth pipe 14 from the branch unit 2 is connected to the indoor heat exchanger 15 The other side of the indoor heat exchanger 15 is connected to one side of the indoor-side electronic expansion valve 17, and the other side of the indoor-side electronic expansion valve 17 is connected to the fifth pipe 16 from the flow dividing unit 2. It is connected. A bypass pipe 19 having an on-off control valve 20 formed of an electromagnetic valve is connected to both ends of the third on-off valve 12 in the flow dividing unit 2. Further, a pressure sensor (or pressure switch) 23 for detecting a refrigerant pressure is provided in a pipe of each indoor heat exchanger 15, and the pressure sensor 23 is connected to a control unit (microcomputer) 22 provided on the indoor unit side. The opening and closing of the open / close control valve 20 is controlled by a command from the control unit 22.

Next, the operation of the present invention in the above configuration will be described. In FIG. 1, a description will be given of a state in which the indoor unit 3a performs the heating operation, the indoor unit 3b is in the stopped state, and the indoor unit 3c starts the heating operation. Open the second on-off valve 11 and the third on-off valve 12 of the indoor unit 3a,
The first on-off valve 9 and the fourth on-off valve 13 of the indoor unit 3a
As a result, the high-temperature and high-pressure refrigerant vapor discharged from the compressor 4 passes through the first pipe 7 and enters the indoor heat exchanger 15 of the indoor unit 3a, as indicated by a solid line arrow. By radiating heat into the room and warming the room in the exchanger 15, the high-temperature and high-pressure refrigerant vapor condenses into a high-temperature and high-pressure refrigerant liquid, and expands at the indoor-side electronic expansion valve 17 to become a low-temperature and low-pressure refrigerant liquid. And enters the outdoor heat exchanger 5 through the third pipe 10, and absorbs and evaporates outdoor heat in the outdoor heat exchanger 5 to become low-temperature and low-pressure refrigerant vapor. And is sucked into the compressor 4 through the compressor 4
The refrigerant is compressed into a high-temperature and high-pressure refrigerant vapor to form one refrigeration cycle, and the indoor unit 3a is operated for heating.

On the other hand, when the heating operation is started from the stopped state of the indoor unit 3c, the third opening / closing valve 12 and the fourth opening / closing valve 13 corresponding to the indoor unit 3c are closed, and the opening / closing control valve 20 is opened. . The high-pressure refrigerant on the discharge side of the compressor 4 passes through the bypass pipe 19 and is applied with pressure to the indoor heat exchanger 15 via the on-off control valve 20, as indicated by a dashed arrow. Then, after a lapse of a predetermined time set in the control unit 22 in advance, the electronic expansion valve 16 on the indoor side is opened to accelerate the pressurization by the liquid pressure. Thereafter, the refrigerant pressure of the indoor heat exchanger is increased to a predetermined pressure (for example, 1.96). (MPa), the opening / closing control valve 20 is closed and the third opening / closing valve 12 is controlled to open, so that the indoor unit 3c can perform the heating operation without generating the refrigerant noise. Indoor unit 3a
Is returned to the flow compressor 4 in the same manner as described above. In addition, the fifth pipe
Since the pressurization is performed by the two pressurizing means of the liquid pipe 16 and the bypass pipe 19, the rise time of the heating operation can be shortened.

FIG. 2 is a configuration diagram of a refrigerant circuit in another embodiment of the multi-room air conditioner according to the present invention. A bypass pipe 19 having a series circuit of an on-off control valve 20 composed of an electromagnetic valve and a capillary tube 18 is connected to both ends of each of the third on-off valves 12 in the flow dividing units 2a, 2b, 2c. Is provided with a pressure sensor (or pressure switch) 25 for detecting the refrigerant pressure, and is connected to a control unit (microcomputer) 22 provided on the indoor unit side.
Controls the opening and closing of each valve.

When the heating operation is started from the stopped state of the indoor unit 3c, the third opening / closing valve 12 and the fourth opening / closing valve 13 corresponding to the indoor unit 3c are closed, and the opening / closing control valve 20 is opened. The high-pressure refrigerant on the discharge side of the compressor 4 passes through the bypass pipe 19 and is applied to the indoor heat exchanger 15 via the on-off control valve 20 and the capillary tube 18 as indicated by the dashed arrow. Then, in advance, the control unit 22
After the elapse of the predetermined time set to, the electronic expansion valve 16 on the indoor side is opened to accelerate pressurization by hydraulic pressure, and then the refrigerant pressure of the indoor heat exchanger detected by the pressure sensor 23,
When the pressure difference of the refrigerant pressure of the first pipe (discharge gas pipe) 7 on the discharge side detected by the pressure sensor 25 becomes small (for example, 0.5 MPa), the on-off control valve 20 is closed, and the third on-off valve is closed. By controlling to open 12, the indoor unit 3c can perform the heating operation without generating the refrigerant noise,
The refrigerant flows back to the compressor 4 in the same manner as the indoor unit 3a. Further, since the pressurization is performed by the two pressurizing means of the fifth pipe 16 (liquid pipe) and the bypass pipe 19, the rise time of the heating operation can be shortened as described above.

Also, as shown in FIG.
A plurality of branch units 2a, 2b, corresponding to the plurality of indoor units 3a, 3b, 3c, respectively, each including a bypass pipe 19 having the third on-off valve 12, the fourth on-off valve 13, the on-off control valve 20, and the like.
By adopting the configuration of 3c, it can be installed at any location according to each indoor unit, and the convenience of installation can be improved. Further, an oil separator 21 is provided on the discharge side of the compressor 4 for separating oil and returning the oil to the suction side of the compressor 4, so that the refrigerating machine oil can be circulated effectively.

As described above, a bypass pipe 19 having an open / close control valve 20 or a series circuit of an open / close control valve 20 and a capillary tube 18 is provided at both ends of the third open / close valve 12 in the flow dividing unit 2. Connect, when starting the heating operation of the stopped indoor unit, while closing the third on-off valve 12 and fourth on-off valve 13 corresponding to the indoor unit, open the on-off control valve 20, after a predetermined time, The indoor side electronic expansion valve 16 is opened, and after the refrigerant pressure of the indoor heat exchanger 5 reaches a predetermined pressure, or when the pressure difference between the refrigerant pressure of the indoor heat exchanger 5 and the refrigerant pressure of the first pipe 7 becomes small. By controlling the opening / closing control valve 20 to close and opening the third opening / closing valve, efficient operation is enabled without flowing refrigerant to the stopped indoor unit, and the indoor unit starts heating operation. Pressure when It can prevent the occurrence of refrigerant noise arising from, and a multi-room air conditioning apparatus capable of shortening the rise time of the heating operation.

[0026]

As described above, according to the present invention,
By connecting an on-off control valve or a bypass pipe provided with a series circuit of an on-off control valve and a capillary tube to both ends of each of the third on-off valves in the branching unit, the efficiency of the refrigerant is reduced without flowing the refrigerant to the stopped indoor unit. Enables good driving,
A multi-room air conditioner that can prevent the generation of refrigerant noise caused by the pressure difference when the indoor unit starts the heating operation and can shorten the rise time of the heating operation.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram showing an embodiment of a multi-room air conditioner according to the present invention.

FIG. 2 is a refrigerant circuit diagram showing another embodiment according to the present invention.

FIG. 3 is a refrigerant circuit diagram of a conventional multi-room air conditioner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outdoor unit 2 Branching unit 3a, 3b, 3c Indoor unit 4 Compressor 5 Outdoor heat exchanger 6 Electronic expansion valve outside a room 7 First piping 8 Second piping 9 First opening / closing valve 10 Third piping 11 Second opening / closing valve 12 Third open / close valve 13 Fourth open / close valve 14 Fourth pipe 15 Indoor heat exchanger 16 Fifth pipe 17 Indoor electronic expansion valve 18 Capillary tube 19 Bypass pipe 20 Open / close control valve A1 First connection part A2 Second connection part A3 Third connection part 23, 25 Pressure sensor

Claims (7)

[Claims] 1. A branch from a discharge side of a compressor, one of which is connected to a first on-off valve, an outdoor heat exchanger, an electronic expansion valve and a first connection part, and the other of which is connected to a second pipe. Connecting the connecting portion and connecting the third connecting portion to one of the pipelines leading to the suction side of the compressor, and performing the second opening and closing between the other pipeline and the first on-off valve and the outdoor heat exchanger. An outdoor unit to which a valve is connected, a first pipe connected to the second connection portion, a branch from the first pipe, and a plurality of third on-off valves connected in parallel,
A second pipe is connected to the third connection portion, branched from the second pipe, and a plurality of fourth on-off valves are connected in parallel, and the plurality of third on-off valves and the fourth on-off valve are respectively connected in parallel. Each connected to a plurality of fourth pipes connected to, a third pipe connected to the first connection portion, branched from the third pipe, a plurality of fifth pipes connected in parallel, a diversion unit, An indoor heat exchanger from the fourth pipe, a plurality of indoor units connected to the fifth pipe via an indoor-side electronic expansion valve,
By controlling the opening and closing of the first on-off valve, the second on-off valve, the third on-off valve and the fourth on-off valve in accordance with the operation state, a cooling operation and a heating operation are selectively performed for each of the plurality of indoor units, Alternatively, in a multi-room air conditioner configured to be able to perform simultaneous cooling and heating simultaneous operation performed by stopping the outdoor heat exchanger, the third on-off valve in the branch unit In each case, a bypass pipe provided with an open / close control valve is connected to each end, and pressure detection means for detecting a refrigerant pressure is provided in a pipe of each indoor heat exchanger, and a heating operation of the stopped indoor unit is started. Closing the third on-off valve and the fourth on-off valve corresponding to the indoor unit, opening the on-off control valve, and after a lapse of a predetermined time, opening the indoor-side electronic expansion valve,
After that, after the refrigerant pressure of the indoor heat exchanger reaches a predetermined pressure, the multi-room air conditioner is controlled to open the third on-off valve. 2. A branch from the discharge side of the compressor, one of which is connected to a first on-off valve, an outdoor heat exchanger, an electronic expansion valve and a first connection part, and the other of which is connected to a second pipe. Connecting the connecting portion and connecting the third connecting portion to one of the pipelines leading to the suction side of the compressor, and performing the second opening and closing between the other pipeline and the first on-off valve and the outdoor heat exchanger. An outdoor unit to which a valve is connected, a first pipe connected to the second connection portion, a branch from the first pipe, and a plurality of third on-off valves connected in parallel,
A second pipe is connected to the third connection portion, branched from the second pipe, and a plurality of fourth on-off valves are connected in parallel, and the plurality of third on-off valves and the fourth on-off valve are respectively connected in parallel. Each connected to a plurality of fourth pipes connected to, a third pipe connected to the first connection portion, branched from the third pipe, a plurality of fifth pipes connected in parallel, a diversion unit, An indoor heat exchanger from the fourth pipe, a plurality of indoor units connected to the fifth pipe via an indoor-side electronic expansion valve,
By controlling the opening and closing of the first on-off valve, the second on-off valve, the third on-off valve and the fourth on-off valve in accordance with the operation state, a cooling operation and a heating operation are selectively performed for each of the plurality of indoor units, Alternatively, in a multi-room air conditioner configured to be able to perform simultaneous cooling and heating simultaneous operation performed by stopping the outdoor heat exchanger, the third on-off valve in the branch unit At both ends of each, a bypass pipe having a series circuit of an open / close control valve and a capillary tube is connected, and pressure detection means for detecting refrigerant pressure is provided on each of the indoor heat exchanger pipes and the bypass pipe, When the heating operation of the stopped indoor unit is started, the third open / close valve and the fourth open / close valve corresponding to the indoor unit are closed, and the open / close control valve is opened. The indoor side electronic expansion valve is opened, and thereafter, after the pressure difference between the refrigerant pressure of the indoor heat exchanger and the refrigerant pressure of the bypass pipe reaches a predetermined value, the third open / close valve is controlled to be opened. Multi-room air conditioner. 3. The multi-room air conditioner according to claim 1, wherein an electromagnetic valve is used as the on-off control valve. 4. The multi-room air conditioner according to claim 1, wherein an electronic expansion valve is used as the opening / closing control valve. 5. The multi-room air conditioner according to claim 1, wherein a pressure sensor or a pressure switch is used as the pressure detecting means. 6. The flow dividing unit comprises a plurality of flow dividing units respectively corresponding to the plurality of indoor units, and each including a bypass pipe having the third on-off valve, the fourth on-off valve, and an on-off control valve. 2. The method according to claim 1, wherein
Or the multi-room air conditioner according to 2. 7. The multi-chamber air conditioner according to claim 1, wherein an oil separator for separating oil and returning the oil to a suction side of the compressor is provided on a discharge side of the compressor. .