Air conditioning system

Abstract

The utility model provides an air conditioning system, and relates to the technical field of air conditioners. The air conditioning system comprises an outdoor unit and a plurality of indoor units, the outdoor unit comprises a compressor, a reversing valve and an outdoor heat exchanger, and the air conditioning system further comprises a first main air pipe, a second main air pipe, a main liquid pipe and a connecting air pipe. Through the arrangement of the connecting gas pipe, the first main gas pipe and the second main gas pipe can be selectively communicated, so that no matter which main gas pipe retains oil at the lower end position, the main gas pipe can be switched through a switching mode; and the first main gas pipe is communicated with the second main gas pipe, so that the oil which is originally retained at the lower end of the main gas pipe is reversely circulated to the compressor again, and the problem of insufficient oil quantity of the compressor is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of air conditioning, and in particular to an air conditioning system. Background Art

[0002] A multi-split air conditioner consists of an outdoor unit and an indoor unit. Under the installation condition where there is a height difference between the outdoor unit and the indoor unit (hereinafter referred to as the internal and external difference), when the gas pipeline is transported upward from low to high, the oil (which can play a role in lubrication and antifreeze) is difficult to move at the same time as the refrigerant, and is thus retained at the lower end of the gas pipeline. This retained oil cannot flow back to the compressor. If it continues to increase, the compressor will be short of oil, and the risk of damage will increase.

[0003] In a three-pipe cooling and heating free machine (i.e., multiple indoor units can operate in different modes), due to the high-pressure gas pipe and the low-pressure gas pipe, the oil in the refrigerant will be retained at the lower end of one of the gas pipes, and by switching the mode, the gaseous refrigerant will also switch to the other gas pipe for operation, so the retained oil cannot be transported back to the compressor. Therefore, it is difficult for the existing three-pipe cooling and heating free machine to solve the problem of oil retention at the lower end of the gas pipe when there is a difference between the inside and the outside. Utility Model Content

[0004] The problem to be solved by the present application is that the oil of the three-pipe free-heating and cooling air-conditioning system is easily retained in the lower part of the air pipe, resulting in insufficient oil in the compressor.

[0005] To solve the above problems, in a first aspect, the present application provides an air conditioning system, comprising an outdoor unit and a plurality of indoor units, the outdoor unit comprising a compressor, a reversing valve and an outdoor heat exchanger, the air conditioning system further comprising a first main air pipe, a second main air pipe, a main liquid pipe and a connecting air pipe, one end of the first main air pipe is connected to the exhaust side of the compressor, and the other end thereof branches out a plurality of first branch pipes which are connected to the plurality of indoor units in a one-to-one correspondence, one end of the second main air pipe is connected to the intake side of the compressor, and the other end thereof branches out a plurality of second branch pipes which are connected to the plurality of indoor units in a one-to-one correspondence, one end of the main liquid pipe is connected to the outdoor heat exchanger, and the other end thereof branches out a plurality of branch liquid pipes which are connected to the plurality of indoor units in a one-to-one correspondence, the outdoor heat exchanger is switchably connected to the exhaust side and the intake side of the compressor through the reversing valve;

[0006] A first valve is provided on the first main air pipe, a second valve is provided on the second main air pipe, one end of the connecting air pipe is connected to the first main air pipe on the side of the first valve away from the compressor, and the other end is connected to the second main air pipe on the side of the second valve away from the compressor, and an oil return valve is provided on the connecting air pipe.

[0007] In the embodiment of the present application, by setting a connecting air pipe between the first main air pipe and the second main air pipe, the first main air pipe and the second main air pipe can be selectively connected. The first main air pipe and the second main air pipe can be connected, so that no matter which main air pipe has oil retained at the lower end position, the refrigerant in the air pipe with oil retained can be reversed (from top to bottom) by switching the mode, so as to transport the retained oil back to the compressor. For example, if the outdoor unit is located at a low position relative to the indoor unit, then the end of the first main air pipe close to the outdoor unit is prone to retain oil during heating operation. At this time, in order to recover the oil, it is only necessary to switch to the cooling mode and keep the first main air pipe and the second main air pipe connected through the connecting air pipe. In this way, at least a part of the low-pressure gaseous refrigerant passing through the indoor unit can flow along the first main air pipe to the compressor. This process will pass through the area where the oil is retained. The low-pressure gaseous refrigerant can carry the oil and flow to the second main air pipe through the connecting air pipe, and then return to the compressor. The traditional three-pipe cooling and heating free machine cannot pass the low-pressure gaseous refrigerant through the first main air pipe under cooling conditions (because the first main air pipe only serves as a high-pressure main air pipe), so it cannot bring back the oil retained in the first main air pipe. Similarly, when the outdoor unit is located at a high position relative to the indoor unit, the end of the second main air pipe close to the indoor unit is prone to retain oil during cooling operation. At this time, in order to recover the oil, it is only necessary to switch to heating mode and keep the first main air pipe and the second main air pipe connected through the connecting air pipe. In this way, the high-pressure gaseous refrigerant passing through the exhaust side of the compressor can first flow along the first main air pipe, and when passing through the connecting air pipe, at least a part of the gaseous refrigerant flows into the second main air pipe through the connecting air pipe. The high-pressure gaseous refrigerant in the second main air pipe moves downward to the area where the oil is retained, and enters the indoor unit with the oil, releases heat and liquefies into liquid refrigerant. The ability of liquid refrigerant to drive the oil to flow is much stronger than that of gaseous refrigerant. Therefore, the liquid refrigerant can enter the outdoor unit from bottom to top along the liquid cooling pipe with the oil, first pass through the outdoor heat exchanger, and then return to the compressor to achieve oil return.

[0008] When the oil return valve is closed and the first valve and the second valve are opened, the first main air pipe acts as a high-pressure air pipe and the second main air pipe acts as a low-pressure air pipe, which can realize free adjustment of the heating and cooling of the air conditioning system (that is, some indoor units can cool and some indoor units can heat at the same time). When the outdoor unit is at a low position, the oil is retained at the lower end of the first main air pipe, so when the oil is returned, the oil return valve is opened to connect the first main air pipe and the second main air pipe, and the first valve is closed and the second valve is opened; when the outdoor unit is at a high position, the oil is retained at the lower end of the second main air pipe, so when the oil is returned, the oil return valve is opened to connect the first main air pipe and the second main air pipe, and the first valve is opened and the second valve is closed.

[0009] In an optional embodiment, the oil return valve is a solenoid valve.

[0010] In an optional implementation, the first valve and the second valve are solenoid valves.

[0011] In an optional embodiment, the inner diameter of the connecting air pipe and the caliber of the oil return valve are both larger than the inner diameter of the first main air pipe. By setting the inner diameter of the connecting air pipe and the caliber of the oil return valve larger, sufficient refrigerant flow can be ensured during oil return operation, thereby improving the oil return effect.

[0012] In an optional embodiment, the caliber of the first valve is larger than the inner diameter of the first main air pipe, and the caliber of the second valve is larger than the inner diameter of the second main air pipe. By setting the caliber of the first valve larger than the inner diameter of the first main air pipe, the condensation temperature drop of the heating indoor unit caused by the pressure drop can be avoided; and by setting the caliber of the second valve larger than the inner diameter of the second main air pipe, the suction pressure drop of the compressor caused by the pressure drop can be avoided when there is a cooling indoor unit.

[0013] In an optional embodiment, the air conditioning system further includes a controller, the first valve, the second valve and the oil return valve are all electrically connected to the controller, and the controller is used to receive the height difference information between the outdoor unit and the indoor unit and control the first valve, the second valve and the oil return valve to switch the flow path. The height difference information includes which of the indoor unit and the outdoor unit is at a relatively high or low position. By receiving the height difference information between the outdoor unit and the indoor unit by the controller, the air conditioning system can automatically control the control strategy of each valve during the oil return operation according to the height difference information.

[0014] In an optional embodiment, the outdoor unit further includes an outdoor expansion valve disposed on the main liquid pipe.

[0015] In an optional embodiment, an internal expansion valve is provided on each branch liquid pipe.

[0016] In an optional embodiment, a first switching valve is provided on the first bronchus, and a second switching valve is provided on the second bronchus. Since the air conditioning system of the embodiment of the present application is a three-pipe cooling and heating free machine, the gaseous refrigerant can be controlled to be transported from the first bronchus or the second bronchus by selectively controlling one of the first switching valve and the second switching valve to open.

[0017] In an optional embodiment, the reversing valve is a four-way reversing valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of an air conditioning system in the related art when the outdoor unit is in a high position;

[0019] Figure 2 It is a schematic diagram of an air conditioning system in the related art when the outdoor unit is in a low position;

[0020] Figure 3 This is a schematic diagram of oil return of an air-conditioning system according to an embodiment of the present application when the outdoor unit is at a high position;

[0021] Figure 4 This is a schematic diagram of oil return of an air-conditioning system according to an embodiment of the present application when the outdoor unit is in a low position.

[0022] Explanation of the reference numerals: 100-outdoor unit; 110-compressor; 120-reversing valve; 130-outdoor heat exchanger; 140-connecting air pipe; 141-first valve; 142-second valve; 143-return oil valve; 150-extension valve of outdoor unit; 200-indoor unit; 210-indoor heat exchanger; 220-expansion valve of indoor unit; 300-manifold box; 310-first switching valve; 320-second switching valve; 400-first main air pipe; 410-first bronchial pipe; 500-second main air pipe; 510-second bronchial pipe; 600-main liquid pipe; 610-branch liquid pipe. DETAILED DESCRIPTION

[0023] Figure 1 It is a schematic diagram of an air conditioning system in the related art when the outdoor unit is in a high position; Figure 2 FIG. 1 is a schematic diagram of an air conditioning system in the related art when the outdoor unit is in a low position. Figure 1 and Figure 2 As shown, in the three-pipe free-cooling and heating air conditioning system in the related art, when there is a height difference between the outdoor unit and the indoor unit, the oil in the high-pressure main air pipe or the low-pressure main air pipe will be retained at the lower end of the air pipe and difficult to circulate back to the compressor. The main reason for this problem is that the gaseous refrigerant is much weaker than the liquid refrigerant in its ability to drive the oil to move together. Therefore, when the gaseous refrigerant moves from bottom to top, it is difficult for the oil to move upward with the gaseous refrigerant and it will be at the lower end of the air pipe under the action of gravity. Figure 1 As shown, when the outdoor unit is in a high position, during heating operation, the high-pressure main air pipe transports high-pressure gaseous refrigerant from top to bottom. The liquid refrigerant after passing through the indoor unit goes up and returns to the compressor after passing through the outdoor heat exchanger. Since the liquid refrigerant in the main liquid pipe goes up, oil retention is not likely to occur. However, when operating in cooling mode, the high-pressure gaseous refrigerant first passes through the outdoor heat exchanger and is converted into liquid refrigerant that flows along the main liquid pipe. After reaching the indoor unit, it is converted into low-pressure gaseous refrigerant and transported upward along the low-pressure main air pipe back to the outdoor unit. In the process of the low-pressure gaseous refrigerant going up along the low-pressure main air pipe, it is difficult for the oil to follow the gaseous refrigerant upward, so it will be retained in the low-pressure main air pipe at one end close to the indoor unit. Figure 2In the outdoor unit, the outdoor unit is located at a low position. During cooling operation, the liquid refrigerant in the main liquid pipe goes up, and the gaseous refrigerant in the low-pressure main air pipe goes down, so it is not easy to have the problem of oil retention. However, when operating in heating mode, the high-pressure gaseous refrigerant is transported upward along the high-pressure main air pipe to the indoor unit, and the oil will be retained in the high-pressure main air pipe near the end of the outdoor unit. It can be seen that in the traditional three-pipe cooling and heating free air conditioning system, the main air pipe is divided into two types: high-pressure main air pipe and low-pressure main air pipe. The high-pressure main air pipe only transports high-pressure gaseous refrigerant, and the flow direction is always from the outdoor unit to the indoor unit, while the low-pressure main air pipe only transports low-pressure gaseous refrigerant, and the flow direction is always from the indoor unit to the outdoor unit. Therefore, as long as there is a height difference between the outdoor unit and the indoor unit, oil will be retained at the low end of one of the main air pipes, and it is impossible to achieve oil return by switching the mode to rely on the refrigerant reverse circulation. The traditional oil return method is to increase the power of the compressor, speed up the refrigerant flow rate in the air pipe, and thus improve the ability of the gaseous refrigerant to carry oil back to the outdoor unit. However, in the main air pipe with upward flow, it is difficult to return oil even if the compressor runs at a high speed. Therefore, in the prior art, the three-pipe free cooling and heating air conditioning system with internal and external height difference is prone to insufficient oil in the compressor.

[0024] In order to improve the problem of difficulty in oil return in the existing three-pipe type cooling and heating free air-conditioning system, the embodiment of the present application provides an air-conditioning system, which increases a connecting air pipe on the outdoor unit to achieve that both high-pressure refrigerant and low-pressure refrigerant can flow in the two main air pipes. Compared with the traditional three-pipe type cooling and heating free air-conditioning system, when returning the oil, the gaseous refrigerant can be selected to "reverse" in the main air pipe with retained oil, thereby achieving oil return.

[0025] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0026] Figure 3 This is a schematic diagram of oil return of an air conditioning system according to an embodiment of the present application when the outdoor unit 100 is located at a high position; Figure 4 Schematic diagram of oil return of an air conditioning system in an embodiment of the present application when the outdoor unit 100 is in a low position. Figure 3 and Figure 4As shown, the present application provides an air-conditioning system, including an outdoor unit 100 and multiple indoor units 200, the outdoor unit 100 includes a compressor 110, a reversing valve 120 and an outdoor heat exchanger 130, the air-conditioning system also includes a first main air pipe 400, a second main air pipe 500, a main liquid pipe 600 and a connecting air pipe 140, one end of the first main air pipe 400 is connected to the exhaust side of the compressor 110, and the other end is divided into a plurality of first branch pipes 410 connected to the multiple indoor units 200 in a one-to-one correspondence, one end of the second main air pipe 500 is connected to the intake side of the compressor 110, and the other end is divided into a plurality of second branch pipes 510 connected to the multiple indoor units 200 in a one-to-one correspondence, one end of the main liquid pipe 600 is connected to the outdoor heat exchanger 130, and the other end is divided into a plurality of branch liquid pipes 610 connected to the multiple indoor units 200 in a one-to-one correspondence, and the outdoor heat exchanger 130 is switchably connected to the exhaust side and the intake side of the compressor 110 through the reversing valve 120. The connecting air pipe 140 connects the first main air pipe 400 and the second main air pipe 500 .

[0027] In this embodiment, the indoor unit 200 includes an indoor heat exchanger 210, and the branch liquid pipe 610 and the gas pipe connected to the indoor unit 200 described above are both connected to the indoor heat exchanger 210. The indoor unit 200 also includes an indoor expansion valve 220, which is arranged on the branch liquid pipe 610, and the outdoor unit 100 also includes an outdoor expansion valve 150 arranged on the main liquid pipe 600, and the indoor expansion valve 220 and the outdoor expansion valve 150 are used to throttle the liquid refrigerant. The reversing valve 120 in this embodiment is a four-way reversing valve, and the reversing valve 120 can change the working condition of the outdoor heat exchanger 130 (i.e., as an evaporator or a condenser) by switching, thereby controlling the air conditioning system to operate mainly in heating or cooling.

[0028] Furthermore, the first bronchial tube 410 is provided with a first switching valve 310, and the second bronchial tube 510 is provided with a second switching valve 320. By selectively controlling one of the first switching valve 310 and the second switching valve 320 to open, the gaseous refrigerant can be controlled to be transported from the first bronchial tube 410 or the second bronchial tube 510. Figure 3 and Figure 4It can be seen that the air conditioning system provided in the embodiment of the present application is a three-pipe cooling and heating free air conditioning system, that is, at the same time, some indoor units 200 can be cooled and the other indoor units 200 can be heated. For example, the air conditioning system is mainly operated for heating, that is, the outdoor heat exchanger 130 is used as an evaporator. At this time, the high-pressure gaseous refrigerant output from the exhaust side of the compressor 110 passes through the first main air pipe 400, the first branch pipe 410, the indoor heat exchanger 210, the branch liquid pipe 610, and the outdoor heat exchanger 130 in sequence, and finally returns to the compressor 110 to realize the heating cycle. In this process, the first switching valve 310 corresponding to the indoor unit 200 in heating operation is opened, and the second switching valve 320 is closed. When one of the indoor units 200 needs to switch to the cooling mode, there is no need to control the reversing valve 120 to switch, and the outdoor heat exchanger 130 still remains as an evaporator. It is only necessary to open the second switching valve 320 corresponding to the indoor unit 200 that needs to switch to the cooling mode, and close the first switching valve 310. At this time, the liquid refrigerant flowing out of the heating-running indoor unit 200 will flow along the branch liquid pipe 610 to the branch liquid pipe 610 corresponding to the indoor unit 200 that needs cooling, realizing evaporation heat absorption (i.e. cooling) in the indoor unit 200, and the formed low-pressure gaseous refrigerant will return to the compressor 110 along the second main air pipe 500.

[0029] In this embodiment, each of the first switching valve 310 and the second switching valve 320 is accommodated in one branch box 300 .

[0030] In the embodiment of the present application, a first valve 141 is provided on the first main air pipe 400, a second valve 142 is provided on the second main air pipe 500, one end of the connecting air pipe 140 is connected to the first main air pipe 400 on the side of the first valve 141 away from the compressor 110, and the other end is connected to the second main air pipe 500 on the side of the second valve 142 away from the compressor 110, and an oil return valve 143 is provided on the connecting air pipe 140. By providing the oil return valve 143, the first main air pipe 400 and the second main air pipe 500 can be selectively connected.

[0031] By providing the connecting air pipe 140, the first main air pipe 400 and the second main air pipe 500 can be connected, so that no matter which main air pipe has oil retained at the lower end, the refrigerant in the air pipe with oil retained can be reversed (from top to bottom) by switching the mode, so as to transport the retained oil back to the compressor 110. Figure 3In the embodiment, the outdoor unit 100 is at a high position, and the air conditioning system is in normal cooling operation (the first valve 141 and the second valve 142 are open, the oil return valve 143 is closed, the first switching valve 310 is closed, and the second switching valve 320 is open), which will cause oil to be retained at the lower end of the second main air pipe 500. Then, in order to return the oil, the oil return valve 143 is opened, and the first main air pipe 400 and the second main air pipe 500 are connected by the connecting air pipe 140, and the first valve 141 is opened and the second valve 142 is closed. Then the air conditioning system is controlled to switch to heating, the first switching valve 310 and the second switching valve 320 are opened, and then a part of the high-pressure gaseous refrigerant will enter the second main air pipe 500 from the first main air pipe 400 through the connecting air pipe 140, and pass through the second branch pipe 510, the indoor heat exchanger 210, the branch liquid pipe 610, the main liquid pipe 600, the outdoor heat exchanger 130 in sequence, and then return to the compressor 110 (such as Figure 3 In this cycle, the high-pressure gaseous refrigerant brings the oil retained at the lower end of the second main air pipe 500 to the indoor unit 200, and the gaseous refrigerant is converted into liquid refrigerant and transported back to the compressor 110 with the oil to achieve oil return. It can be understood that in addition to the part of the high-pressure gaseous refrigerant that enters the second main air pipe 500 through the connecting air pipe 140, another part of the high-pressure gaseous refrigerant flows from the first main air pipe 400 to the indoor unit 200 (the same as in normal operation). Since the lower end of the first main air pipe 400 does not retain oil, in other optional embodiments, the first switching valve 310 can be closed so that all the high-pressure gaseous refrigerant enters the second main air pipe 500 through the connecting air pipe 140.

[0032] For example Figure 4 In the embodiment, the outdoor unit 100 is at a low position, and the air conditioning system is operating normally for heating (the first valve 141 and the second valve 142 are open, the oil return valve 143 is closed, the first switching valve 310 is open, and the second switching valve 320 is closed), which may cause oil to be retained at the lower end of the first main air pipe 400. In order to return the oil, the oil return valve 143 is opened, and the first main air pipe 400 and the second main air pipe 500 are connected by the connecting air pipe 140, and the first valve 141 is closed and the second valve 142 is opened. Then the air conditioning system is controlled to switch to cooling, the first switching valve 310 and the second switching valve 320 are opened, and the high-pressure gas refrigerant will first pass through the outdoor heat exchanger 130 to become a liquid refrigerant, and then pass through the main liquid pipe 600, the branch liquid pipe 610, the first branch pipe 410 and the second branch pipe 510, the first main air pipe 400 and the second main air pipe 500 in sequence, and then the refrigerant in the first main air pipe 400 is merged into the second main air pipe 500 through the connecting air pipe 140, and then returns to the compressor 110 (such as Figure 4Indicated by the middle arrow). During this cycle, the low-pressure gaseous refrigerant brings the oil retained at the lower end of the first main air pipe 400 to the compressor 110 to achieve oil return. In the above-mentioned oil return operation cycle, part of the low-pressure gaseous refrigerant sent from the indoor unit 200 enters the first main air pipe 400, and part enters the second main air pipe 500, while the lower end of the second main air pipe 500 does not retain oil. Therefore, in other optional embodiments, the second switching valve 320 can also be closed to allow all refrigerants to pass through the first main air pipe 400, the connecting air pipe 140, the second main air pipe 500 in sequence, and then return to the compressor.

[0033] When the air conditioning system is operating normally, the oil return valve 143 can be closed and the first valve 141 and the second valve 142 can be opened. The first main air pipe 400 is used as a high-pressure air pipe, and the second main air pipe is used as a low-pressure air pipe 500, so that the air conditioning system can be freely adjusted in temperature (that is, some indoor units 200 can be cooled and some indoor units 200 can be heated at the same time). Therefore, under normal operating conditions, the flow direction of the gaseous refrigerant in the first main air pipe 400 and the second main air pipe 500 can be directional, and the high-pressure gaseous refrigerant in the first main air pipe 400 always flows from the outdoor unit 100 to the indoor unit 200, and the low-pressure gaseous refrigerant in the second main air pipe 500 always flows from the indoor unit 200 to the outdoor unit 100. When the outdoor unit 100 is at a low position, oil is retained at the lower end of the first main air pipe 400, so the oil return valve 143 is opened when the oil is returned, connecting the first main air pipe 400 and the second main air pipe 500, and the first valve 141 is closed and the second valve 142 is opened; when the outdoor unit 100 is at a high position, oil is retained at the lower end of the second main air pipe 500, so the oil return valve 143 is opened when the oil is returned, connecting the first main air pipe 400 and the second main air pipe 500, and the first valve 141 is opened and the second valve 142 is closed.

[0034] Furthermore, the oil return valve 143 , the first valve 141 , the second valve 142 , the first switching valve 310 , and the second switching valve 320 may be solenoid valves.

[0035] Furthermore, the inner diameter of the connecting air pipe 140 and the caliber of the oil return valve 143 are both larger than the inner diameter of the first main air pipe 400. By setting the inner diameter of the connecting air pipe 140 and the caliber of the oil return valve 143 larger, sufficient refrigerant flow can be ensured during oil return operation, thereby improving the oil return effect.

[0036] Furthermore, the caliber of the first valve 141 is larger than the inner diameter of the first main air pipe 400, and the caliber of the second valve 142 is larger than the inner diameter of the second main air pipe 500. By setting the caliber of the first valve 141 to be larger than the inner diameter of the first main air pipe 400, the condensation temperature drop of the heating indoor unit 200 caused by the pressure drop can be avoided; and by setting the caliber of the second valve 142 to be larger than the inner diameter of the second main air pipe 500, the suction pressure drop of the compressor 110 caused by the pressure drop can be avoided when there is a cooling indoor unit 200.

[0037] In this embodiment, the air conditioning system further includes a controller (not shown in the figure), and the first valve 141, the second valve 142 and the oil return valve 143 are all electrically connected to the controller, and the controller is used to receive the height difference information between the outdoor unit 100 and the indoor unit 200 and control the first valve 141, the second valve 142 and the oil return valve 143 to switch the flow path. The height difference information includes which of the indoor unit 200 and the outdoor unit 100 is at a relatively high or low position. By receiving the height difference information between the outdoor unit 100 and the indoor unit 200 through the controller, the air conditioning system can automatically control the control strategy of the first valve 141, the second valve 142 and the oil return valve 143 during the oil return operation according to the height difference information. Specifically, the height difference information of the outdoor unit 100 can be input through a wired controller or a DIP switch, and the controller will receive and record this information and perform corresponding control.

[0038] In summary, the air-conditioning system provided in the embodiment of the present application includes an outdoor unit and multiple indoor units, the outdoor unit includes a compressor, a reversing valve and an outdoor heat exchanger, the air-conditioning system also includes a first main air pipe, a second main air pipe, a main liquid pipe and a connecting air pipe, one end of the first main air pipe is connected to the exhaust side of the compressor, and the other end is divided into multiple first branch pipes connected to the multiple indoor units one-to-one, one end of the second main air pipe is connected to the suction side of the compressor, and the other end is divided into multiple second branch pipes connected to the multiple indoor units one-to-one, one end of the main liquid pipe is connected to the outdoor heat exchanger, and the other end is divided into multiple branch liquid pipes connected to the multiple indoor units one-to-one, the outdoor heat exchanger is switchably connected to the exhaust side and the suction side of the compressor through the reversing valve; a first valve is provided on the first main air pipe, a second valve is provided on the second main air pipe, one end of the connecting air pipe is connected to the first main air pipe on the side of the first valve away from the compressor, and the other end is connected to the second main air pipe on the side of the second valve away from the compressor, and an oil return valve is provided on the connecting air pipe. By setting up a connecting air pipe, the first main air pipe and the second main air pipe can be selectively connected, so that no matter which main air pipe has oil retained at the lower end, the mode can be switched and the first main air pipe and the second main air pipe can be connected to allow the oil originally retained at the lower end of the main air pipe to circulate back to the compressor, thereby avoiding the problem of insufficient oil in the compressor.

[0039] Although the present application is disclosed as above, the present application is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, the protection scope of the present application shall be subject to the scope defined by the claims.

Claims

1. An air conditioning system, characterized in that: The air conditioning system comprises an outdoor unit (100) and a plurality of indoor units (200), wherein the outdoor unit (100) comprises a compressor (110), a reversing valve (120) and an outdoor heat exchanger (130), and the air conditioning system further comprises a first main air pipe (400), a second main air pipe (500), a main liquid pipe (600) and a connecting air pipe (140), wherein one end of the first main air pipe (400) is connected to the exhaust side of the compressor (110), and the other end thereof is divided into a plurality of first branch air pipes (410) which are connected to the plurality of indoor units (200) in a one-to-one correspondence. One end of the second main air pipe (500) is connected to the air intake side of the compressor (110), and the other end thereof branches out a plurality of second branch pipes (510) which are connected one-to-one to the plurality of indoor units (200); one end of the main liquid pipe (600) is connected to the outdoor heat exchanger (130), and the other end thereof branches out a plurality of branch liquid pipes (610) which are connected one-to-one to the plurality of indoor units (200); the outdoor heat exchanger (130) is switchably connected to the exhaust side and the air intake side of the compressor (110) via the reversing valve (120); The first main air pipe (400) is provided with a first valve (141), the second main air pipe (500) is provided with a second valve (142), one end of the connecting air pipe (140) is connected to the first main air pipe (400) on a side of the first valve (141) away from the compressor (110), and the other end is connected to the second main air pipe (500) on a side of the second valve (142) away from the compressor (110), and the connecting air pipe (140) is provided with an oil return valve (143).

2. The air conditioning system according to claim 1, characterized in that: The oil return valve (143) is a solenoid valve.

3. The air conditioning system according to claim 1, characterized in that: The first valve (141) and the second valve (142) are solenoid valves.

4. The air conditioning system according to claim 1, characterized in that: The inner diameter of the connecting air pipe (140) and the caliber of the oil return valve (143) are both larger than the inner diameter of the first main air pipe (400).

5. The air conditioning system according to claim 1, characterized in that: The caliber of the first valve (141) is larger than the inner diameter of the first main air pipe (400), and the caliber of the second valve (142) is larger than the inner diameter of the second main air pipe (500).

6. The air conditioning system according to any one of claims 1 to 5, characterized in that: The air conditioning system further comprises a controller, the first valve (141), the second valve (142) and the oil return valve (143) are all electrically connected to the controller, and the controller is used to receive height difference information between the outdoor unit (100) and the indoor unit (200) and control the first valve (141), the second valve (142) and the oil return valve (143) to switch flow paths.

7. The air conditioning system according to any one of claims 1 to 5, characterized in that: The outdoor unit (100) further includes an outdoor unit expansion valve (150) disposed on the main liquid pipe (600).

8. The air conditioning system according to any one of claims 1 to 5, characterized in that: Each of the branch liquid pipes (610) is provided with an internal machine expansion valve (220).

9. The air conditioning system according to any one of claims 1 to 5, characterized in that: The first bronchus (410) is provided with a first switching valve (310), and the second bronchus (510) is provided with a second switching valve (320).

10. The air conditioning system according to any one of claims 1 to 5, characterized in that: The reversing valve (120) is a four-way reversing valve.

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