Outdoor unit working mode switching method and three-pipe type multi-split air conditioning system

Abstract

The invention provides an outdoor unit working mode switching method and a three-pipe type multi-split air conditioning system. The method comprises the following steps: entering a switching control process according to heating and refrigerating demand change information; after the switching control process is entered, the current working mode of an outdoor unit in the three-pipe type air conditioning system is obtained; when the current working mode is the main refrigeration mode, a first switching index is obtained, and if the first switching index is smaller than or equal to a first preset value, a first mode switching instruction is output to instruct a four-way reversing valve in the three-pipe type air conditioning system to reverse; and when the current working mode is the main heating mode, a second switching index is obtained, and if the second switching index is larger than or equal to a second preset value, a second mode switching instruction is output to instruct the four-way reversing valve to reverse. The refrigerating or heating effect of the outdoor unit is efficiently adjusted in real time according to the change of the indoor refrigerating requirement or the indoor heating requirement.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning, and in particular to a method for switching working modes of an outdoor unit and a three-pipe multi-connected air conditioning system. Background Art

[0002] A three-pipe air conditioning system is a system that enables simultaneous cooling and heating of indoor units. It consists of multiple indoor units, each connected to an outdoor unit via high-pressure gas pipes, low-pressure gas pipes, and liquid pipes. Users can configure each indoor unit to operate in independent cooling or heating mode, allowing some units to operate in cooling mode while others operate in heating mode, providing significant convenience.

[0003] Typically, a three-pipe air conditioning system determines the heating effect of the heating indoor unit based on the exhaust pressure of the outdoor unit's compressor, the operating gear of the outdoor unit's fan, and the opening of the heating indoor unit's electronic expansion valve, and determines the cooling effect of the cooling indoor unit based on the opening of the cooling indoor unit's electronic expansion valve. The system then adjusts the refrigerant amounts of the heating indoor unit and the cooling indoor unit accordingly to compensate for the cooling or heating effect.

[0004] However, when the indoor cooling demand or heating demand changes, if the above method is used to determine whether the original cooling or heating effect meets the new cooling demand or heating demand before making adjustments, the efficiency is low and the real-time performance is insufficient. Summary of the Invention

[0005] In response to the deficiencies in the prior art, the present invention provides a method for switching the working mode of an outdoor unit and a three-pipe multi-split air-conditioning system, which solves the problems in the prior art of not being able to directly adjust the cooling or heating effect of the outdoor unit according to changes in indoor cooling or heating demand, resulting in low efficiency and insufficient real-time performance.

[0006] According to an embodiment of the present invention, a first aspect provides a method for switching an outdoor unit operating mode, which is applied to a three-pipe air conditioning system. The method includes:

[0007] Enter the switching control process according to the change information of heating and cooling demand;

[0008] After entering the switching control process, the current working mode of the outdoor unit of the three-pipe air conditioning system is obtained;

[0009] When the current operating mode is the main cooling mode, obtaining a first switching indicator corresponding to the main cooling mode, the first switching indicator being a compressor exhaust pipe temperature in the three-pipe air conditioning system; if the first switching indicator is less than or equal to a first preset value, outputting a first mode switching instruction, the first mode switching instruction instructing the four-way reversing valve in the three-pipe air conditioning system to reverse and switch the operating mode of the outdoor unit from the main cooling mode to the main heating mode;

[0010] When the current working mode is the main heating mode, a second switching index corresponding to the main heating mode is obtained, and the second switching index is the temperature of the compressor suction pipe in the three-pipe air-conditioning system; if the second switching index is greater than or equal to a second preset value, a second mode switching instruction is output, and the second mode switching instruction instructs the four-way reversing valve to reverse and switch the working mode of the outdoor unit from the main heating mode to the main cooling mode.

[0011] Optionally, after entering the switching control process, the current ambient temperature is also detected;

[0012] If the current ambient temperature is less than or equal to the preset temperature value and the current working mode is mainly heating mode, then obtaining a third switching index, wherein the third switching index is the average liquid pipe temperature of the indoor units in the three-pipe air-conditioning system that are turned on in cooling mode;

[0013] If the third switching indicator is greater than or equal to a third preset value, a second mode switching instruction is output.

[0014] Optionally, before entering the switching control process according to the heating and cooling demand change information, the process includes:

[0015] If, in a three-pipe air-conditioning system, the ratio between the number of indoor units entering heating mode or the number of indoor units entering cooling mode at the current moment is different from the ratio at the previous moment, and the change in the ratio is greater than the preset change threshold, the heating and cooling demand change information is obtained.

[0016] Optionally, after entering the switching control process, when a first switching indicator corresponding to the main cooling mode is obtained, the operating gear of the outdoor fan in the three-pipe air-conditioning system is reduced.

[0017] Optionally, the lowest operating gear of the outdoor fan is 0.

[0018] Optionally, after entering the switching control process, when obtaining the second switching index corresponding to the main heating mode, the operating gear of the outdoor fan in the three-pipe air-conditioning system is reduced or the opening of the outdoor unit electronic expansion valve in the three-pipe air-conditioning system is reduced.

[0019] Optionally, the lowest operating gear of the outdoor fan is 0, and the lowest opening degree of the electronic expansion valve is 0.

[0020] A second aspect provides a three-pipe multi-split air conditioning system, comprising N groups of three-pipe air conditioning systems;

[0021] Each three-pipe air conditioning system includes an outdoor unit, multiple indoor units, and a four-way reversing valve control module; the outdoor unit includes an outdoor heat exchanger, an outdoor fan adjacent to the outdoor heat exchanger, an outdoor unit electronic expansion valve, a four-way reversing valve, a one-way valve, a compressor, a compressor exhaust pipe, and a compressor intake pipe; the four-way reversing valve control module includes a solenoid pilot valve connected to the four-way reversing valve, a main control board that controls the solenoid pilot valve, a temperature sensor located in the compressor exhaust pipe and a temperature sensor located in the compressor intake pipe connected to the main control board;

[0022] Each indoor unit is connected to a one-way valve via a high-pressure gas pipe, which is in turn connected to a four-way reversing valve, which is also connected to an outdoor heat exchanger. Each indoor unit is also connected to a four-way reversing valve via a low-pressure gas pipe, and is then connected to an outdoor unit electronic expansion valve and an outdoor heat exchanger in sequence via a liquid pipe.

[0023] The temperature sensor located in the compressor exhaust pipe provides a first switching index, the temperature sensor located in the compressor suction pipe provides a second switching index, and the main control board implements the outdoor unit mode switching method as described in claims 1 to 7.

[0024] Optionally, the four-way reversing valve control module further includes an ambient temperature sensor connected to the main control board for detecting the current ambient temperature.

[0025] Optionally, the four-way reversing valve includes an S port, a C port, a D port and an E port;

[0026] In the main cooling mode, the four-way reversing valve is in a first connected state, the S port is connected to the indoor unit through a low-pressure air pipe and is connected to the compressor suction pipe through the low-pressure air pipe, the E port is connected to the S port and is connected to the low-pressure air pipe through the electromagnetic pilot valve, the C port is connected to the D port and is connected to the outdoor heat exchanger, and the D port is connected to the compressor exhaust pipe through a high-pressure air pipe and is connected to the input end of the one-way valve;

[0027] In the main heating mode, the four-way reversing valve is in the second connection state, the S port is connected to the indoor unit through the low-pressure gas pipe and is connected to the compressor suction pipe through the low-pressure gas pipe, the C port is connected to the S port and is connected to the outdoor heat exchanger, the D port is connected to the compressor exhaust pipe and is connected to the input end of the one-way valve, and the E port is connected to the D port and is connected to the low-pressure gas pipe through the electromagnetic pilot valve; according to the first switching instruction, when the working mode of the outdoor unit is switched from the main cooling mode to the main heating mode, the four-way reversing valve is switched from the first connection state to the second connection state;

[0028] When the working mode of the outdoor unit is switched from the main heating mode to the main cooling mode according to the second switching instruction, the four-way reversing valve is switched from the second connection state to the first connection state.

[0029] Compared with the prior art, the present invention has the following beneficial effects: when the indoor unit has both cooling and heating demands, it is judged whether the heating demand in the main cooling mode increases or the cooling demand decreases according to the first switching index and the first preset value, that is, the compressor exhaust pipe temperature and the high pressure value set according to the ideal high pressure saturation temperature, so that the working mode of the outdoor unit is switched from the main cooling mode to the main heating mode through the first mode switching instruction, and the priority of the heating effect in the three-pipe air-conditioning system is corrected; or it is judged whether the cooling demand in the main heating mode increases or the heating demand decreases according to the second switching index and the second preset value, that is, the compressor suction pipe temperature and the low pressure value set according to the ideal low pressure saturation temperature, so that the working mode of the outdoor unit is switched from the main heating mode to the main cooling mode through the second mode switching instruction, and the priority of the cooling effect in the three-pipe air-conditioning system is corrected. After obtaining the information on changes in heating and cooling demand, the above process can directly switch the working mode of the outdoor unit and adjust the priority of cooling and heating effects. The switching efficiency is high and the response is fast, thereby meeting the cooling and heating demands corresponding to the current state of the three-pipe air-conditioning system in real time, achieving better cooling and heating effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the implementation flow of the method for switching the working mode of an outdoor unit according to an embodiment of the present invention;

[0031] Figure 2 Schematic diagram of the implementation flow of another outdoor unit working mode switching method according to an embodiment of the present invention;

[0032] Figure 3 Schematic diagram of logic judgment of the handover control process shown in step S103 according to an embodiment of the present invention;

[0033] Figure 4 Schematic diagram of logic judgment of the handover control process shown in step S104 according to an embodiment of the present invention;

[0034] Figure 5 This is a structural diagram of a group of three-pipe air-conditioning systems in a three-pipe multi-split air-conditioning system according to an embodiment of the present invention;

[0035] Figure 6 This is a structural diagram of a three-pipe air-conditioning system in the main cooling mode according to an embodiment of the present invention;

[0036] Figure 7 Schematic diagram of the structure of a three-pipe air-conditioning system in main cooling mode according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0038] like Figure 1 As shown, an embodiment of the present invention proposes a method for switching the working mode of an outdoor unit, which is applied to a three-pipe air conditioning system, including but not limited to the following steps:

[0039] S101, entering the switching control process according to the heating and cooling demand change information;

[0040] S102: After entering the switching control process, obtain the working mode of the outdoor unit in the three-pipe air conditioning system;

[0041] S103: When the current operating mode is the main cooling mode, obtaining a first switching indicator corresponding to the main cooling mode, the first switching indicator being a compressor exhaust pipe temperature in the three-pipe air conditioning system; if the first switching indicator is less than or equal to a first preset value, outputting a first mode switching instruction, the first mode switching instruction instructing a four-way reversing valve in the three-pipe air conditioning system to reverse and switch the operating mode of the outdoor unit from the main cooling mode to the main heating mode;

[0042] S104. When the current working mode is the main heating mode, obtain a second switching index corresponding to the main heating mode, where the second switching index is the temperature of the compressor suction pipe in the three-pipe air-conditioning system; if the second switching index is greater than or equal to a second preset value, output a second mode switching instruction, where the second mode switching instruction instructs the four-way reversing valve to reverse and switch the working mode of the outdoor unit from the main heating mode to the main cooling mode.

[0043] Regarding step S101 above, in a specific application, a three-pipe air conditioning system includes one outdoor unit and multiple indoor units, each of which has its own independent cooling or heating mode. Therefore, the heating and cooling demand change information is generated based on the ratio between the number of indoor units entering heating mode or the number of indoor units entering cooling mode at two adjacent moments. Therefore, before step S101 above, the following steps are included:

[0044] If, in a three-pipe air-conditioning system, the ratio between the number of indoor units entering heating mode or the number of indoor units entering cooling mode at the current moment is different from the ratio at the previous moment, and the change in the ratio is greater than the preset change threshold, the heating and cooling demand change information is obtained.

[0045] It can be understood that the difference between the ratio of the number of indoor units entering the heating mode or the number of indoor units entering the cooling mode at the current moment and the ratio at the previous moment, that is, the above-mentioned change amount, is within the range of the preset change threshold, such as 0 to 0.1, indicating that the ratio of the number of indoor units entering the heating mode or the number of indoor units entering the cooling mode at the current moment is the same as the ratio at the previous moment. Conversely, outside the preset change threshold, such as greater than 0.1, indicating that the ratio of the number of indoor units entering the heating mode or the number of indoor units entering the cooling mode at the current moment is different from the ratio at the previous moment, and the heating and cooling demand change information is output at this time. The above-mentioned step S101 can obtain the heating and cooling demand change information.

[0046] It should be noted that the current moment and the previous moment represent two adjacent moments, and the time interval between any two adjacent moments can be set according to the actual application scenario. For example, in the application scenario of an office building, the time interval between two adjacent moments in the working time period is shorter than the time interval between two adjacent moments in the non-working time period.

[0047] In step S102, the outdoor unit's current operating mode includes a primary cooling mode and a primary heating mode. Steps S103 and S104 are described based on the outdoor unit's operating mode switching method when the current operating mode is the primary cooling mode or the current operating mode is the primary heating mode, respectively.

[0048] In step S103, the first switching indicator is the compressor exhaust pipe temperature in the three-pipe air conditioning system. This is directly obtained data, but in actual use, when comparing it with the first preset value, the compressor exhaust pipe temperature needs to be converted to a high-pressure value. Furthermore, in an embodiment of the present invention, the first preset value is set based on the high-pressure value corresponding to the ideal high-pressure saturation temperature. For example, if the outdoor unit is in main cooling mode and the ideal compressor exhaust pipe temperature, i.e., the ideal high-pressure saturation temperature, is 44-48°C, then the first preset value is the high-pressure value A = 2450 kPa, corresponding to the preset high-pressure saturation temperature A' = 42°C. The comparison between the first switching indicator and the first preset value is to determine whether the first switching indicator is less than or equal to 2450 kPa, i.e., the preset high-pressure saturation temperature A' = 42°C.

[0049] Similarly, in step S104 above, the second switching indicator is the compressor suction pipe temperature in the three-pipe air conditioning system. This is directly obtained data, but in actual use, when comparing it with the second preset value, the compressor suction pipe temperature needs to be converted to a low-pressure value. Furthermore, in an embodiment of the present invention, the second preset value is set based on the low-pressure value corresponding to the ideal low-pressure saturation temperature. For example, if the outdoor unit is in primary heating mode and the ideal compressor suction pipe temperature, i.e., the ideal low-pressure saturation temperature, is 2-8°C, then the second preset value is the low-pressure value B = 980 kPa corresponding to the preset low-pressure saturation temperature B' = 10°C. The comparison between the second switching indicator and the second preset value is to determine whether the second switching indicator is greater than or equal to 980 kPa, i.e., the preset low-pressure saturation temperature B' = 10°C.

[0050] In a preferred implementation, when the switching control process is entered in step S103 and a first switching index corresponding to the primary cooling mode is obtained, the operating gear of the outdoor fan is first lowered to avoid the influence of the outdoor fan connected to the outdoor heat exchanger in the three-pipe air conditioning system, i.e., the influence of the outdoor fan on the first switching index. Similarly, when the switching control process is entered in step S104 and a second switching index corresponding to the primary heating mode is obtained, the operating gear of the outdoor fan is first lowered or the opening of the outdoor electronic expansion valve is reduced to avoid the influence of the outdoor fan and the influence of the outdoor electronic expansion valve on the second switching index in the three-pipe air conditioning system.

[0051] It should be noted that, since the main method for controlling the compressor exhaust pressure in the main cooling mode is the outdoor unit fan, therefore, during the switching control process, if necessary, such as when it is necessary to reduce the sensitivity of the outdoor unit working mode switching while maintaining a certain compressor exhaust pressure, the operating gear of the outdoor fan can be adjusted to the lowest value of 0. In the main heating mode, the main methods for controlling the compressor suction pressure are the outdoor unit fan and the outdoor unit electronic expansion valve. Therefore, during the switching control process, if necessary, such as when it is necessary to reduce the sensitivity of the outdoor unit working mode switching while maintaining a low compressor suction pressure, the operating gear of the outdoor fan can be adjusted to the lowest value of 0, or the opening of the outdoor unit electronic expansion valve can be adjusted to the lowest value of 0.

[0052] Furthermore, in specific applications, to prevent pressure fluctuations during compressor frequency changes, a first mode switch command is output when the first switching indicator remains less than a first preset value for a duration greater than a preset determination time. A second mode switch command is output when the second switching indicator remains greater than a second preset value for a duration greater than a preset determination time. Furthermore, with respect to the third switching indicator in the following embodiment, to prevent liquid pipe temperature fluctuations during expansion valve regulation, a second mode switch command is also output when the third switching indicator remains greater than a third preset value for a duration greater than a preset determination time. In a preferred implementation, this preset determination time is 5 minutes.

[0053] Through the above steps S101 to S104, the embodiment of the present invention determines whether the heating demand in the main cooling mode increases or the cooling demand decreases according to the first switching index and the first preset value, that is, the compressor exhaust pipe temperature and the high pressure value set according to the ideal high pressure saturation temperature, when the indoor unit has both cooling and heating demands. Thus, the working mode of the outdoor unit is switched from the main cooling mode to the main heating mode through the first mode switching instruction, and the priority of the heating effect in the three-pipe air-conditioning system is corrected; or determines whether the cooling demand in the main heating mode increases or the heating demand decreases according to the second switching index and the second preset value, that is, the compressor suction pipe temperature and the low pressure value set according to the ideal low pressure saturation temperature. Thus, the working mode of the outdoor unit is switched from the main heating mode to the main cooling mode through the second mode switching instruction, and the priority of the cooling effect in the three-pipe air-conditioning system is corrected. After obtaining the information on changes in heating and cooling demand, the above process can directly switch the working mode of the outdoor unit and adjust the priority of cooling and heating effects. The switching efficiency is high and the response is fast, thereby meeting the cooling and heating demands that are adapted to the current state of the three-pipe air-conditioning system in real time, achieving better cooling and heating effects.

[0054] like Figure 2 As shown, another embodiment of the present invention provides a method for switching an outdoor unit working mode, including: Figure 1 The outdoor unit working mode switching method shown in FIG. 1 includes steps S201 to S204, which are identical to steps S101 to S104 and are not described in detail here. The method further includes the following steps:

[0055] S205: After entering the switching control process, the current ambient temperature is also detected;

[0056] If the current ambient temperature is less than or equal to the preset temperature value and the current working mode is mainly heating mode, then obtaining a third switching index, wherein the third switching index is the average liquid pipe temperature of the indoor units in the three-pipe air-conditioning system that are turned on in cooling mode;

[0057] If the third switching indicator is greater than or equal to a third preset value, a second mode switching instruction is output.

[0058] In a better implementation, the above-mentioned preset temperature value is 10°C, and the third preset value is set to 10°C based on the average liquid pipe temperature of the indoor unit normally turned on in cooling mode when the ambient temperature is lower than 10°C. When the third switching index is greater than or equal to the third preset value, it means that in the main heating mode, there are indeed indoor units turned on in cooling mode, and the number is relatively large, thereby outputting the heating and cooling demand change information.

[0059] Therefore, according to the above step S205, the embodiment of the present invention also solves the problem that when the ambient temperature is lower than 10°C and the main heating mode is running, the low-pressure saturation temperature value is usually lower than 10°C, which easily leads to the second mode switching instruction not being outputted by mistake.

[0060] like Figure 3 and Figure 4 As shown, the embodiment of the present invention describes the implementation of the switching control process shown in step S103 and the switching control process shown in step S104. First, it is assumed that the four-way reversing valve includes a first connection state OFF and a second connection state ON. Then, Figure 3 To implement the switching control process shown in step S103, when the working mode of the outdoor unit is the main cooling mode, the four-way reversing valve is in the first connection state OFF. If the first switching index is less than or equal to the first preset value A'=2450kpa (that is, the high-pressure saturation temperature A=42°C), the four-way reversing valve is reversed from the first connection state OFF to the second connection state ON, indicating that the working mode of the outdoor unit is switched from the main cooling mode to the main heating mode. Figure 4 To implement the switching control process shown in step S104, the working mode of the outdoor unit is the main heating mode. At this time, the four-way reversing valve is in the second connection state ON. First, the current ambient temperature is detected. If the current ambient temperature is less than or equal to the preset temperature value, such as 10°C, it is determined whether the third switching index is greater than or equal to the third preset value C'. When the third switching index is greater than or equal to the third preset value C', the four-way reversing valve is switched from the second connection state ON to the first connection state OFF, indicating that the working mode of the outdoor unit is switched from the main heating mode to the main cooling mode; if the ambient temperature is greater than the preset temperature value, such as 10°C, the second switching index and the second preset value are determined. When the second switching index is greater than or equal to the second preset value B'=980kpa (i.e., low-pressure saturation temperature B=10°C), the four-way reversing valve is switched from the second connection state ON to the first connection state OFF, which also indicates that the working mode of the outdoor unit is switched from the main heating mode to the main cooling mode.

[0061] The embodiment of the present invention further provides a three-pipe multi-split air conditioning system, comprising N groups of three-pipe air conditioning systems; Figure 5 As shown, each three-pipe air conditioning system includes an outdoor unit 10, multiple indoor units 20, and a four-way reversing valve control module; the outdoor unit 10 includes an outdoor heat exchanger 11, an outdoor unit electronic expansion valve 12, an outdoor fan 13 adjacent to the outdoor heat exchanger 11, a four-way reversing valve 14, a one-way valve 15, and a compressor 16. The compressor 16 includes a compressor exhaust pipe 161 connected to the four-way reversing valve 14 and a compressor intake pipe 162 connected to the four-way reversing valve 14; the four-way reversing valve control module includes a solenoid pilot valve 31 connected to the four-way reversing valve, a main control board (not shown) that controls the solenoid pilot valve, a temperature sensor 32 located in the compressor exhaust pipe 161 connected to the main control board, and a temperature sensor 33 located in the compressor intake pipe 162;

[0062] Each indoor unit 20 is connected to a one-way valve 15 via a high-pressure gas pipe a, and the one-way valve 15 is connected to a four-way reversing valve 14. Each indoor unit is also connected to the four-way reversing valve 14 via a low-pressure gas pipe b, and is sequentially connected to the outdoor unit electronic expansion valve 12 and the outdoor heat exchanger 11 via a liquid pipe c. The four-way reversing valve 14 is connected to the outdoor heat exchanger 11 via the low-pressure gas pipe b or the high-pressure gas pipe a.

[0063] Among them, the temperature sensor 32 located in the compressor exhaust pipe provides a first switching index, and the temperature sensor 33 located in the compressor intake pipe provides a second switching index. The main control board implements the outdoor unit mode switching method described in the above embodiment, and outputs the first mode switching instruction or the second mode switching instruction to the solenoid pilot valve.

[0064] In one embodiment, the four-way reversing valve control module further includes an ambient temperature sensor connected to the main control board for detecting the current ambient temperature. This ambient temperature sensor is used to address the issue of the low-pressure saturation temperature typically being below 10°C when the primary heating mode is in operation, which can lead to the erroneous failure to output the second mode switching instruction.

[0065] It is understandable that the connection between the main control board and the temperature sensor located in the compressor exhaust duct, the temperature sensor located in the compressor intake duct, and the ambient temperature sensor can be an electrical connection or a wireless connection, which is not limited in the embodiments of the present invention.

[0066] The embodiment of the present invention is Figure 6 and Figure 7 , through a three-pipe air conditioning system, the above-mentioned four-way reversing valve 14 is connected to the outdoor heat exchanger 11 through the low-pressure gas pipe b or the high-pressure gas pipe a, which is described. However, it can be understood that if Figure 5The three-pipe air conditioning system shown is the simplest structure and may also include peripheral components such as filters and lubricating oil systems. The embodiment of the present invention includes them in the following examples: Figure 6 and Figure 7 The detailed structure of the three-pipe air conditioning system is shown.

[0067] in, Figure 6 and Figure 7 The four-way reversing valve shown in FIG includes port S, port C, port D and port E; Figure 6 As shown, exemplarily, in the main cooling mode, the four-way reversing valve is in the first connected state, the S port is connected to the indoor unit 20 through the low-pressure gas pipe and is connected to the compressor suction pipe 162 through the low-pressure gas pipe, the E port is connected to the S port and is connected to the low-pressure gas pipe through the electromagnetic pilot valve 31, the C port is connected to the D port and is connected to the outdoor heat exchanger 11, and the D port is connected to the compressor exhaust pipe 161 through the high-pressure gas pipe and is connected to the input end of the one-way valve 15. Figure 7 As shown, exemplarily, in the main heating mode, the four-way reversing valve is in the second connected state, the S port is connected to the indoor unit 20 through the low-pressure air pipe and is connected to the compressor suction pipe 162 through the low-pressure air pipe, the C port is connected to the S port and is connected to the outdoor heat exchanger 11, the D port is connected to the compressor exhaust pipe 161 and is connected to the input end of the one-way valve 15, and the E port is connected to the D port and is connected to the low-pressure air pipe through the electromagnetic pilot valve 31.

[0068] In an embodiment of the present invention, according to the first switching instruction, when the working mode of the outdoor unit is switched from the main cooling mode to the main heating mode, the four-way reversing valve is switched from the first connected state to the second connected state; according to the second switching instruction, when the working mode of the outdoor unit is switched from the main heating mode to the main cooling mode, the four-way reversing valve is switched from the second connected state to the first connected state.

[0069] Figure 6 and Figure 7 The detailed structure of the indoor unit is also shown in FIG. 1 , wherein the electronic expansion valve of the indoor unit that enters the heating mode and the indoor unit that enters the cooling mode, i.e., the indoor unit electronic expansion valve is open. Figure 6 and Figure 7 The working principle of the above three-pipe multi-split air conditioning system in actual application, especially the method for implementing the outdoor unit mode switching as described above by the main control board, is described, including:

[0070] (1) The current working mode of the outdoor unit is the main cooling mode. After the refrigerant comes out of the compressor exhaust pipe, it is divided into two parts. One part enters the outdoor heat exchanger through the four-way reversing valve, becomes liquid refrigerant after heat dissipation, enters the liquid pipe, and then enters the indoor unit with cooling demand after throttling through the indoor unit electronic expansion valve, absorbs heat, and then returns to the S port through the low-pressure valve in the refrigerant converter; the other part of the refrigerant coming out of the exhaust pipe passes through the one-way valve and then enters the indoor unit with heating demand through the high-pressure valve in the refrigerant converter. After heat dissipation in the indoor unit, it becomes liquid refrigerant and enters the liquid pipe. It is then mixed with the liquid refrigerant after heat dissipation in the outdoor heat exchanger and enters the indoor unit;

[0071] During the operation of the three-pipe air-conditioning system, the indoor heating demand increases / cooling demand decreases, and the main cooling mode will not be able to meet the heating demand. At this time, it is necessary to correct the priority of the heating effect in the three-pipe air-conditioning system. The specific operation is to reverse the four-way reversing valve in the manner shown in the above embodiment, such as Figure 1 Step S103 shown in FIG. Figure 2 Step S203 shown in FIG. Figure 3 The switching control process is realized in the main cooling mode shown in FIG. In this case, the three-pipe air conditioning system before the four-way reversing valve is switched is as follows Figure 6 As shown, the three-pipe air conditioning system after the four-way reversing valve is switched is as follows Figure 7 shown.

[0072] (2) The current working mode of the outdoor unit is mainly heating mode. After the refrigerant comes out of the compressor exhaust pipe, it passes through the one-way valve and then enters the indoor unit with heating demand through the high-pressure valve in the refrigerant converter. After the refrigerant in the indoor unit dissipates heat, it enters the liquid pipe and is divided into two parts. One part enters the outdoor heat exchanger, absorbs heat and returns to the S port through the C port of the four-way reversing valve. The other part enters the indoor unit with cooling demand after throttling through the indoor unit electronic expansion valve, absorbs heat and returns to the S port through the low-pressure valve of the refrigerant converter.

[0073] During the operation of the three-pipe air-conditioning system, the indoor heating demand decreases / the cooling demand increases, and the main heating mode will not be able to meet the cooling demand. At this time, it is necessary to correct the priority of the cooling effect in the three-pipe air-conditioning system. The specific operation is to reverse the four-way reversing valve in the manner shown in the above embodiment, such as Figure 1 Step S104 shown in FIG. Figure 2 Steps S204 and S205 shown in FIG. Figure 4 The switching control process is realized in the main cooling mode shown in FIG. In this case, the three-pipe air conditioning system before the four-way reversing valve is switched is as follows Figure 7 As shown, the three-pipe air conditioning system after the four-way reversing valve is switched is as follows Figure 6 shown.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for switching an outdoor unit working mode, characterized in that: Applied to a three-pipe air conditioning system, the method includes: Enter the switching control process according to the change information of heating and cooling demand; After entering the switching control process, the current working mode of the outdoor unit of the three-pipe air conditioning system is obtained; When the current operating mode is the main cooling mode, obtaining a first switching indicator corresponding to the main cooling mode, the first switching indicator being a compressor exhaust pipe temperature in the three-pipe air conditioning system; if the first switching indicator is less than or equal to a first preset value, outputting a first mode switching instruction, the first mode switching instruction instructing the four-way reversing valve in the three-pipe air conditioning system to reverse and switch the operating mode of the outdoor unit from the main cooling mode to the main heating mode; When the current working mode is the main heating mode, a second switching index corresponding to the main heating mode is obtained, and the second switching index is the temperature of the compressor suction pipe in the three-pipe air-conditioning system; if the second switching index is greater than or equal to a second preset value, a second mode switching instruction is output, and the second mode switching instruction instructs the four-way reversing valve to reverse and switch the working mode of the outdoor unit from the main heating mode to the main cooling mode.

2. The outdoor unit operation mode switching method according to claim 1, wherein: After entering the switching control process, the current ambient temperature is also detected; If the current ambient temperature is less than or equal to the preset temperature value and the current working mode is mainly heating mode, then obtaining a third switching index, wherein the third switching index is the average liquid pipe temperature of the indoor units in the three-pipe air-conditioning system that are turned on in cooling mode; If the third switching indicator is greater than or equal to a third preset value, a second mode switching instruction is output.

3. The outdoor unit operation mode switching method according to claim 1 or 2, characterized in that: Before entering the switching control process based on the heating and cooling demand change information, it includes: If, in a three-pipe air-conditioning system, the ratio between the number of indoor units entering heating mode or the number of indoor units entering cooling mode at the current moment is different from the ratio at the previous moment, and the change in the ratio is greater than the preset change threshold, the heating and cooling demand change information is obtained.

4. The outdoor unit operation mode switching method according to claim 1, wherein: After entering the switching control process, when a first switching index corresponding to the main cooling mode is obtained, the operating gear of the outdoor fan in the three-pipe air-conditioning system is reduced.

5. The outdoor unit operation mode switching method according to claim 4, wherein: The lowest operating gear of the outdoor fan is 0.

6. The outdoor unit operation mode switching method according to claim 1, wherein: After entering the switching control process, when obtaining the second switching index corresponding to the main heating mode, the operating gear of the outdoor fan in the three-pipe air-conditioning system is reduced or the opening of the outdoor unit electronic expansion valve in the three-pipe air-conditioning system is reduced.

7. The outdoor unit operation mode switching method according to claim 6, wherein: The lowest operating gear of the outdoor fan is 0, and the lowest opening degree of the electronic expansion valve is 0.

8. A three-pipe multi-split air conditioning system, characterized in that: Including N sets of three-pipe air conditioning systems; Each three-pipe air conditioning system includes an outdoor unit, multiple indoor units, and a four-way reversing valve control module; the outdoor unit includes an outdoor heat exchanger, an outdoor fan adjacent to the outdoor heat exchanger, an outdoor unit electronic expansion valve, a four-way reversing valve, a one-way valve, and a compressor; the compressor includes a compressor exhaust pipe connected to the four-way reversing valve and a compressor intake pipe connected to the four-way reversing valve; the four-way reversing valve control module includes a solenoid pilot valve connected to the four-way reversing valve, a main control board that controls the solenoid pilot valve, a temperature sensor located in the compressor exhaust pipe connected to the main control board, and a temperature sensor located in the compressor intake pipe; Each indoor unit is connected to a one-way valve via a high-pressure gas pipe, which is in turn connected to a four-way reversing valve, which is also connected to an outdoor heat exchanger. Each indoor unit is also connected to a four-way reversing valve via a low-pressure gas pipe, and is then connected to an outdoor unit electronic expansion valve and an outdoor heat exchanger in sequence via a liquid pipe. The temperature sensor located in the compressor exhaust pipe provides a first switching index, the temperature sensor located in the compressor suction pipe provides a second switching index, and the main control board implements the outdoor unit mode switching method as described in claims 1 to 7.

9. The three-pipe multi-split air conditioning system according to claim 8, wherein: The four-way reversing valve control module further includes an ambient temperature sensor connected to the main control board for detecting the current ambient temperature.

10. The three-pipe multi-split air conditioning system according to claim 8, wherein: The four-way reversing valve includes an S port, a C port, a D port and an E port; In the main cooling mode, the four-way reversing valve is in a first connected state, the S port is connected to the indoor unit through a low-pressure air pipe and is connected to the compressor suction pipe through the low-pressure air pipe, the E port is connected to the S port and is connected to the low-pressure air pipe through the electromagnetic pilot valve, the C port is connected to the D port and is connected to the outdoor heat exchanger, and the D port is connected to the compressor exhaust pipe through a high-pressure air pipe and is connected to the input end of the one-way valve; In the main heating mode, the four-way reversing valve is in the second connection state, the S port is connected to the indoor unit through the low-pressure gas pipe and is connected to the compressor suction pipe through the low-pressure gas pipe, the C port is connected to the S port and is connected to the outdoor heat exchanger, the D port is connected to the compressor exhaust pipe and is connected to the input end of the one-way valve, and the E port is connected to the D port and is connected to the low-pressure gas pipe through the electromagnetic pilot valve; according to the first switching instruction, when the working mode of the outdoor unit is switched from the main cooling mode to the main heating mode, the four-way reversing valve is switched from the first connection state to the second connection state; When the working mode of the outdoor unit is switched from the main heating mode to the main cooling mode according to the second switching instruction, the four-way reversing valve is switched from the second connection state to the first connection state.

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