Control method for multi-split air conditioning system and multi-split air conditioning system

Abstract

The present application relates to a control method and a multi-split air conditioning system. The control method comprises: when the multi-split air conditioning system is in a cold-blast prevention mode, controlling an indoor unit expansion valve of an indoor unit of the multi-split air conditioning system receiving a start signal to be fully opened; detecting a coil temperature of each of the indoor units starting; comparing the detected coil temperature with a preset temperature threshold, and determining whether the coil temperature of all the indoor units starting exceeds the preset temperature threshold; when the determination result is no, keeping the indoor unit expansion valve of the indoor unit whose coil temperature does not exceed the preset temperature threshold fully opened, and reducing the opening degree of the indoor unit expansion valve of the indoor unit whose coil temperature exceeds the preset temperature threshold. The multi-split air conditioning system can shorten the duration of the cold-blast prevention mode and improve the user experience.

Description

Technical Field

[0001] This invention relates to the field of air conditioning technology, and more specifically to a control method for a multi-split air conditioning system and a multi-split air conditioning system. Background Technology

[0002] A multi-split air conditioning system typically consists of one outdoor unit and N indoor units (N being an integer greater than 1) connected to that outdoor unit. During operation, the user may randomly activate one, two, three, or N indoor units as needed. The outdoor unit includes a compressor, a four-way valve, an outdoor heat exchanger, and an electronic expansion valve, all arranged in the same refrigeration circuit. The outdoor unit may also include more than one compressor to meet larger load demands.

[0003] To improve user experience, existing multi-split air conditioning systems typically implement an anti-cold air mode under low-temperature conditions (such as winter). Specifically, when an indoor unit receives a start-up signal, the outdoor unit's compressor begins operation, while the indoor unit's fan pauses. The fan only restarts once the indoor unit's coil temperature reaches a certain threshold, preventing the air delivered from the indoor unit from becoming too cold. Because refrigerant in a multi-split air conditioning system needs to be distributed to indoor units in different locations via branch pipes, and the capacity and load of each indoor unit may differ, this can lead to discrepancies in the amount of refrigerant flowing into each unit. This phenomenon is commonly referred to as "refrigerant misalignment." Due to refrigerant misalignment, the coil temperatures of different indoor units cannot reach the start-up requirements simultaneously, resulting in an excessively long duration of the anti-cold air mode and a poor user experience.

[0004] Therefore, a new technical solution is needed in this field to solve the above problems. Summary of the Invention

[0005] To address the technical problem of excessively long duration of the anti-cold air mode in existing multi-split air conditioning systems, this invention provides a control method for multi-split air conditioning systems. The control method includes: when the multi-split air conditioning system is in anti-cold air mode, controlling the indoor unit expansion valves of the indoor units of the multi-split air conditioning system that receive a start-up signal to fully open; detecting the coil temperature of each indoor unit that is started up; comparing the measured coil temperature with a preset temperature threshold, and determining whether the coil temperature of all indoor units that are started up exceeds the preset temperature threshold; when the determination result is negative, maintaining the indoor unit expansion valves of the indoor units whose coil temperatures do not exceed the preset temperature threshold fully open, and reducing the opening degree of the indoor unit expansion valves of the indoor units whose coil temperatures exceed the preset temperature threshold.

[0006] In the control method for a multi-split air conditioning system of the present invention, when the multi-split air conditioning system is in anti-cold air mode, the expansion valve of the indoor unit that receives the start-up signal is fully opened to allow refrigerant to flow quickly to each indoor unit. Next, the coil temperature of each indoor unit that is turned on is detected. It should be noted that, unless explicitly stated otherwise, the technical term "indoor unit that is turned on" refers to "the indoor unit that receives the start-up signal," not the indoor unit whose fan is turned on. Then, the measured coil temperature is compared with a preset temperature threshold, and it is determined whether the coil temperature of all indoor units that are turned on exceeds the preset temperature threshold. If the determination result is negative, it means that at least one indoor unit's coil temperature has not yet exceeded the preset temperature threshold. Therefore, the expansion valve of the indoor unit whose coil temperature has not exceeded the preset temperature threshold is kept fully open, and the opening of the expansion valve of the indoor unit whose coil temperature has exceeded the preset temperature threshold is reduced, thereby distributing more refrigerant to the indoor units with lower coil temperatures. Therefore, the control method of the present invention can quickly raise the coil temperature of each indoor unit to a preset temperature threshold by precisely adjusting the opening of the indoor unit expansion valve, reduce the time difference in the coil temperature of each indoor unit to reach the preset temperature threshold, shorten the duration of the anti-cold air mode, and significantly improve the user experience.

[0007] In the preferred embodiment of the control method for a multi-split air conditioning system described above, when the judgment result is yes, the control method further includes: controlling the expansion valve of each indoor unit that is turned on to be fully open, and controlling the multi-split air conditioning system to exit the anti-cold air mode. When the judgment result is yes, it indicates that the coil temperature of all indoor units that are turned on has exceeded the preset temperature threshold. Therefore, controlling the expansion valve of each indoor unit that is turned on to be fully open allows the refrigerant to flow smoothly to each indoor unit, ensuring the cooling efficiency of the entire multi-split air conditioning system.

[0008] In the preferred embodiment of the control method for a multi-split air conditioning system described above, before comparing the measured coil temperature with the preset temperature threshold, the control method further includes: detecting the ambient temperature of the indoor unit to determine the preset temperature threshold, wherein the preset temperature threshold is equal to the sum of the ambient temperature and a first temperature difference. Through the above settings, a corresponding preset temperature threshold can be determined based on the ambient temperature of each indoor unit, thereby improving the user experience.

[0009] In the preferred embodiment of the control method for a multi-split air conditioning system described above, the range of the first temperature difference is 10℃-15℃. This setting ensures that the first temperature difference has a suitable range, preventing both excessively low temperatures that would prevent a good anti-cold-wind effect and excessively high temperatures that would cause the anti-cold-wind mode to last too long.

[0010] In the preferred embodiment of the control method for a multi-split air conditioning system described above, the step of reducing the opening of the indoor unit expansion valve of the indoor unit whose coil temperature exceeds the preset temperature threshold includes: controlling the opening of the indoor unit expansion valve to half of its current opening. Through this setting, the amount of refrigerant flowing to the indoor unit whose coil temperature has exceeded the preset temperature threshold can be rapidly reduced, and the amount of refrigerant flowing to the indoor unit with the lower coil temperature can be correspondingly increased, so that the coil temperature of each indoor unit that is turned on can be quickly raised to the preset temperature threshold.

[0011] In the preferred embodiment of the control method for a multi-split air conditioning system described above, the control method further includes: acquiring the highest and lowest coil temperatures among all the indoor units that are in operation; comparing the sum of the highest coil temperature, the lowest coil temperature, and a second temperature difference; and when the highest coil temperature exceeds the sum, controlling the opening of the indoor unit expansion valve of the indoor unit with the highest coil temperature to half of its current opening. When the highest coil temperature among the indoor units exceeds the sum of the lowest coil temperature and the second temperature difference, it indicates a significant difference between the highest and lowest coil temperatures. Therefore, further controlling the opening of the indoor unit expansion valve of the indoor unit with the highest coil temperature to half of its current opening further shortens the time for all indoor units to heat up synchronously.

[0012] In the preferred embodiment of the control method for a multi-split air conditioning system described above, the range of the second temperature difference is 5℃-8℃. This setting ensures that the second temperature difference has a suitable range, preventing both excessively low temperatures that lead to overly frequent and complex control, and excessively high temperatures that result in untimely control and an inability to achieve rapid temperature equalization.

[0013] In the preferred embodiment of the control method for a multi-split air conditioning system described above, the control method further includes: repeatedly performing the step of detecting the coil temperature of each indoor unit that is turned on after a preset time period. Through the above settings, the coil temperature of the indoor units that are turned on can be continuously detected, thereby more accurately controlling the timing of the anti-cold air mode.

[0014] In the preferred embodiment of the control method for a multi-split air conditioning system described above, the preset time period ranges from 1 min to 2 min. This setting ensures the preset time period has a suitable range, preventing both excessively long periods that could affect control accuracy and excessively short periods that could lead to overly frequent control and compromise system stability.

[0015] To address the technical problem of excessively long duration of the anti-cold air mode in existing multi-split air conditioning systems, this invention provides a multi-split air conditioning system. The control method for multi-split air conditioning systems described above is executed within the multi-split air conditioning system. This invention's multi-split air conditioning system can quickly bring the coil temperature of each indoor unit to a preset temperature threshold, significantly shortening the duration of the anti-cold air mode and substantially improving the user experience. Attached Figure Description

[0016] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0017] Figure 1 This is a system schematic diagram of an embodiment of the multi-split air conditioning system of the present invention;

[0018] Figure 2 This is a flowchart illustrating the control method of the present invention for a multi-split air conditioning system;

[0019] Figure 3 This is a flowchart illustrating the first embodiment of the control method for a multi-split air conditioning system of the present invention;

[0020] Figure 4 This is a flowchart illustrating the second embodiment of the control method for a multi-split air conditioning system of the present invention.

[0021] List of reference numerals in the attached diagram:

[0022] 1. Multi-split air conditioning system; 11. Outdoor unit; 111. Compressor; 112. Gas-liquid separator; 113. Outdoor heat exchanger; 114. Outdoor heat exchanger fan; 115. Distributor; 116. Four-way valve; 117. Liquid shut-off valve; 118. Gas shut-off valve; 119. Gas refrigerant manifold; 120. Liquid refrigerant manifold; 121a. First filter; 121b. Second filter; 121c. Third filter; 121d. Fourth filter; 122a. First outdoor unit expansion valve; 122b. Second outdoor unit expansion valve; 122c. Third outdoor unit expansion valve; 122d. Fourth outdoor unit expansion valve. Expansion valve; 123a, First gas pipe connection branch; 123b, Second gas pipe connection branch; 123c, Third gas pipe connection branch; 123d, Fourth gas pipe connection branch; 124a, First liquid pipe connection branch; 124b, Second liquid pipe connection branch; 124c, Third liquid pipe connection branch; 124d, Fourth liquid pipe connection branch; 125, Exhaust temperature sensor; 126, Outdoor heat exchanger temperature sensor; 127, Defrost sensor; 21, Indoor unit; 211, Indoor heat exchanger; 212, Indoor heat exchanger fan; 213, Indoor heat exchanger temperature sensor; 214, Indoor unit expansion valve. Detailed Implementation

[0023] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0024] It should be noted that in the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "installation," "setting," and "connection" should be interpreted broadly; for example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection, an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0025] To address the technical problem of excessively long duration of the anti-cold air mode in existing multi-split air conditioning systems, this invention provides a control method for a multi-split air conditioning system 1. The control method includes: when the multi-split air conditioning system 1 is in anti-cold air mode, controlling the indoor unit expansion valve 214 of the indoor unit 21 of the multi-split air conditioning system 1 that has received a start-up signal to be fully open (step S1); detecting the coil temperature of each indoor unit 21 that is turned on; comparing the measured coil temperature with a preset temperature threshold, and determining whether the coil temperature of all indoor units 21 that are turned on exceeds the preset temperature threshold; when the determination result is negative, keeping the indoor unit expansion valve 214 of the indoor unit 21 whose coil temperature does not exceed the preset temperature threshold fully open, and reducing the opening degree of the indoor unit expansion valve 214 of the indoor unit 21 whose coil temperature exceeds the preset temperature threshold.

[0026] Figure 1 This is a system schematic diagram of an embodiment of the multi-split air conditioning system of the present invention. Figure 1 As shown, the multi-split air conditioning system 1 of the present invention includes an outdoor unit 11 (generally located in an outdoor environment) that can be interconnected to form a refrigeration circuit allowing refrigerant to flow therethrough, and a plurality of indoor units 21 connected in parallel (generally located indoors or in a room). In one or more embodiments, the multi-split air conditioning system 1 has four indoor units 21 connected in parallel: indoor unit A, indoor unit B, indoor unit C, and indoor unit D. Figure 1 Only indoor unit A is shown; the other three indoor units are omitted. Depending on actual needs, the configuration of the four indoor units can be the same or different. Alternatively, a multi-split air conditioning system 1 can have two, three, or more than four indoor units.

[0027] like Figure 1As shown, in one or more embodiments, the outdoor unit 11 mainly includes a compressor 111, a gas-liquid separator 112, an outdoor heat exchanger 113, an outdoor heat exchanger fan 114, a four-way valve 116, and an outdoor unit expansion valve. Due to the presence of the four-way valve 116, the multi-split air conditioning system 1 of the present invention has at least cooling and heating functions. In one or more embodiments, the compressor 111 is a variable frequency compressor. Alternatively, the compressor 111 may include two or more compressors connected in parallel. These compressors may all be variable frequency compressors, or may include some variable frequency compressors. The compressor 111 has an intake port and an exhaust port (not shown in the figure). The exhaust port of the compressor 111 is connected to the compressor connection port on the four-way valve 116 via a refrigerant pipe (i.e., a pipe that allows refrigerant to flow). An exhaust temperature sensor 125 for measuring the exhaust temperature of the compressor 111 is arranged on the refrigerant pipe near the exhaust port of the compressor 111. The suction port of compressor 111 is connected to the outlet of gas-liquid separator 112 via a refrigerant pipe, while the inlet of gas-liquid separator 112 is connected to the gas-liquid separator connection port of four-way valve 116 via a refrigerant pipe. Four-way valve 116 also has an outdoor heat exchanger connection port and an indoor heat exchanger connection port. One end of outdoor heat exchanger 113 is connected to the outdoor heat exchanger connection port of four-way valve 116 via a refrigerant pipe. Outdoor heat exchanger 113 can be, but is not limited to, a finned coil heat exchanger and a plate heat exchanger, and is equipped with an outdoor heat exchanger fan 114. The other end of outdoor heat exchanger 113 is connected to distributor 115. Outdoor heat exchanger temperature sensor 126 and defrost sensor 127 are also respectively provided on outdoor heat exchanger 113.

[0028] like Figure 1 As shown, the indoor heat exchanger connection port of the four-way valve 116 is connected to the gaseous refrigerant manifold 119 via a refrigerant pipe, and a gas shut-off valve 118 is provided on this refrigerant pipe. The gaseous refrigerant manifold 119 has four gas pipe connection branches: the first gas pipe connection branch 123a, which is configured to connect to indoor unit A; the second gas pipe connection branch 123b, which is configured to connect to indoor unit B; the third gas pipe connection branch 123c, which is configured to connect to indoor unit C; and the fourth gas pipe connection branch 123d, which is configured to connect to indoor unit D. Figure 1As shown, the distributor 115 is connected to the liquid refrigerant manifold 120 via a refrigerant pipe, and a liquid shut-off valve 117 is provided on the refrigerant pipe. The liquid refrigerant manifold 120 has four liquid pipe connection branches: a first liquid pipe connection branch 124a, configured to connect to indoor unit A; a second liquid pipe connection branch 124b, configured to connect to indoor unit B; a third liquid pipe connection branch 124c, configured to connect to indoor unit C; and a fourth liquid pipe connection branch 124d, configured to connect to indoor unit D. A first filter 121a and a first outdoor unit expansion valve 122a are arranged on the first liquid pipe connection branch 124a, wherein the first filter 121a is located between indoor unit A and the first outdoor unit expansion valve 122a. A second filter 121b and a second outdoor unit expansion valve 122b are arranged on the second liquid pipe connection branch 124b, wherein the second filter 121b is located between indoor unit B and the second outdoor unit expansion valve 122b. A third filter 121c and a third outdoor unit expansion valve 122c are arranged on the third liquid pipe connection branch 124c, wherein the third filter 121c is located between the indoor unit C and the third outdoor unit expansion valve 122c. A fourth filter 121d and a fourth outdoor unit expansion valve 122d are arranged on the fourth liquid pipe connection branch 124d, wherein the fourth filter 121d is located between the indoor unit D and the fourth outdoor unit expansion valve 122d.

[0029] like Figure 1 As shown, the indoor unit 21 includes an indoor heat exchanger 211, an indoor heat exchanger fan 212, an indoor heat exchanger temperature sensor 213 for measuring the temperature of the indoor heat exchanger 211, and an indoor unit expansion valve 214. The indoor heat exchanger 211 includes, but is not limited to, a finned-tube heat exchanger. The two ends of the indoor heat exchanger 211 can be connected to a first gas pipe connection branch 123a and a first liquid pipe connection branch 124a, respectively. The indoor unit expansion valve 214 is arranged on the first gas pipe connection branch 123a.

[0030] The multi-split air conditioning system 1 can perform cooling and heating cycles using a four-way valve 116. In the cooling cycle, the outdoor heat exchanger 113 acts as a condenser, while the indoor heat exchanger 211 acts as an evaporator. When the multi-split air conditioning system 1 receives a cooling command, the compressor 111 starts, and the refrigerant (e.g., R134a) is compressed by the compressor 111 and enters the outdoor heat exchanger 113 (which acts as a condenser) in the form of a high-temperature, high-pressure gas through the interconnected ports of the four-way valve 116. In the outdoor heat exchanger 113, the high-temperature, high-pressure gaseous refrigerant is condensed into a high-temperature, high-pressure liquid refrigerant by transferring heat to the airflow caused by the outdoor heat exchanger fan 114. The high-temperature, high-pressure liquid refrigerant flows sequentially through the distributor 115 and the liquid shut-off valve 117 into the liquid refrigerant manifold 120. Then, the high-temperature, high-pressure liquid refrigerant is distributed to one or more of the first, second, third, and fourth liquid pipe connection branches 124a, 124b, 124c, and 124d connected to the already-operated indoor unit, and is expanded into a low-temperature, low-pressure liquid refrigerant by the corresponding outdoor unit expansion valve on the one or more liquid pipe connection branches. This low-temperature, low-pressure liquid refrigerant then flows into the indoor heat exchanger of the already-operated indoor unit 21, such as indoor heat exchanger 211. The low-temperature, low-pressure liquid refrigerant is evaporated into a low-temperature, low-pressure gaseous refrigerant by absorbing heat from the indoor air, thus cooling the indoor air. At this time, the corresponding outdoor unit expansion valve remains fully open, and the refrigerant quantity is regulated by the indoor unit expansion valve 214. After leaving the indoor heat exchanger 211, the low-temperature, low-pressure gaseous refrigerant flows sequentially through the corresponding gas pipe connection branch, gas pipe manifold 119, gas shut-off valve 118, and four-way valve 116, and then enters the gas-liquid separator 112. The gaseous refrigerant, after gas-liquid separation, is then drawn into the compressor 111 through the suction port. A complete refrigeration cycle is thus completed, and this cycle can be performed continuously to achieve the target cooling temperature. Figure 1 As indicated by the arrows, in the heating cycle, the refrigerant flows in the outdoor unit 11 and indoor unit 21 in the opposite direction to that in the cooling cycle. The outdoor heat exchanger 113 acts as the evaporator, while the indoor heat exchanger 211 acts as the condenser. Simultaneously, the corresponding indoor unit expansion valve 214 remains fully open, and the refrigerant quantity is regulated via the outdoor unit expansion valve.

[0031] The control method of the present invention for a multi-split air conditioning system 1 will be described in detail below with reference to any of the above embodiments.

[0032] Figure 2 This is a flowchart illustrating the control method of the present invention for a multi-split air conditioning system. Figure 2As shown, in one or more embodiments, when the control method of the present invention for a multi-split air conditioning system 1 starts, step S1 is first executed. When the multi-split air conditioning system 1 is in anti-cold air mode, the indoor unit expansion valve 214 of the indoor unit 21 of the multi-split air conditioning system 1 that has received the start-up signal is fully opened. Next, step S2 is executed to detect the coil temperature of each indoor unit 21 that is turned on. The coil temperature of the indoor unit 21 can be measured by the indoor heat exchanger temperature sensor 213 arranged on the indoor heat exchanger 211. Then, the control method proceeds to step S3 to compare the measured coil temperature with a preset temperature threshold and determine whether the coil temperature of all indoor units 21 that are turned on exceeds the preset temperature threshold. When the determination result is negative, the indoor unit expansion valve 214 of the indoor unit 21 whose coil temperature does not exceed the preset temperature threshold is kept fully open, and the opening degree of the indoor unit expansion valve 214 of the indoor unit 21 whose coil temperature exceeds the preset temperature threshold is reduced (step S4). With the above settings, the control method of the present invention can quickly raise the coil temperature of each indoor unit 21 to a preset temperature threshold, thereby shortening the duration of cold air protection and significantly improving the user experience.

[0033] Figure 3 This is a flowchart illustrating the first embodiment of the control method for a multi-split air conditioning system according to the present invention. Figure 3As shown, in one or more embodiments, when the control method of the present invention for a multi-split air conditioning system 1 starts, step S1 is first executed. When the multi-split air conditioning system 1 is in anti-cold air mode, the expansion valve 214 of the indoor unit 21 of the multi-split air conditioning system 1 that has received the start-up signal is fully opened. In one or more embodiments, the condition for entering the anti-cold air mode is that the multi-split air conditioning system 1 is in heating mode and the indoor ambient temperature is lower than the preset temperature. The specific value of the preset temperature can be adjusted according to actual needs, for example, 8℃, 10℃, 12℃, etc. Alternatively, the condition for entering the anti-cold air mode can also be adjusted according to actual needs. Next, step S2 is executed to detect the coil temperature of each indoor unit 21 that is turned on. Then, the control method proceeds to step S31 to compare the measured coil temperature with a preset temperature threshold. In one or more embodiments, the preset temperature threshold can be a fixed value, such as 18℃, 20℃, 22℃, etc. That is, it is the same as the preset temperature threshold corresponding to each indoor unit 21 to simplify the control logic. Alternatively, the preset temperature threshold can also be adjusted based on the ambient temperature of the indoor unit 21. In other words, the preset temperature threshold corresponding to each indoor unit 21 may be different. Specifically, before comparing the measured coil temperature with the preset temperature threshold, the control method further includes: detecting the ambient temperature of the indoor unit 21 to determine the preset temperature threshold, wherein the preset temperature threshold is equal to the sum of the ambient temperature and a first temperature difference. In one or more embodiments, the range of the first temperature difference is 10℃-15℃. For example, if the first temperature difference is 10℃, the ambient temperature of indoor unit A is 10℃, and the ambient temperature of indoor unit B is 12℃, then the preset temperature threshold corresponding to indoor unit A is 20℃, and the preset temperature threshold corresponding to indoor unit B is 22℃. After step S31 is completed, the control method executes step S32, that is, determining whether the coil temperature of all powered-on indoor units 21 exceeds the preset temperature threshold. When the judgment result is yes, it means that the coil temperature of all the indoor units 21 that are turned on has exceeded the preset temperature threshold. Therefore, the expansion valve 214 of each indoor unit 21 that is turned on is fully opened, and the multi-split air conditioning system 1 is controlled to exit the anti-cold air mode. After the multi-split air conditioning system 1 exits the anti-cold air mode, the indoor heat exchanger fan 212 of the indoor unit 21 that received the start-up signal operates normally to deliver hot air into the room. The control method ends after step S6 is completed.

[0034] See also Figure 3After step S32 is completed, the control method first executes step S41, which means keeping the indoor unit expansion valve 214 of the indoor unit 21, which maintains the coil temperature below the preset temperature threshold, fully open. Next, the control method executes step S42, which means controlling the opening of the indoor unit expansion valve 214 of the indoor unit 21, which maintains the coil temperature below the preset temperature threshold, to half its current opening. Regarding steps S41 and S42, it should be noted that although this application describes executing S41 first and then S42, this is merely an example. Without departing from the basic principles of this invention, those skilled in the art can arbitrarily adjust the execution order of S41 and S42 as needed, for example, executing S42 first and then S41, or executing both simultaneously. The adjusted solution is equivalent to the technical solution described in this application and therefore falls within the protection scope of this invention.

[0035] See also Figure 3 After step S42 is completed, the control method proceeds to step S5, which involves repeatedly detecting the coil temperature of each indoor unit 21 that is turned on after a preset time period. In one or more embodiments, the preset time period ranges from 1 minute to 2 minutes. For example, the preset time period is 1 minute. After step S5 is completed, the control method re-executes step S31, which involves comparing the re-measured coil temperature with a preset temperature threshold until the coil temperature of all indoor units 21 that are turned on exceeds the preset temperature threshold. Then, the control method controls the indoor unit expansion valve 214 of each indoor unit 21 that is turned on to fully open, and controls the multi-split air conditioning system to exit the anti-cold air mode (i.e., step S6).

[0036] Figure 4 This is a flowchart illustrating the second embodiment of the control method for a multi-split air conditioning system according to the present invention. Figure 4As shown, in one or more embodiments, after step S42 is completed, the control method for a multi-split air conditioning system 1 of the present invention executes step S43, that is, to obtain the highest and lowest coil temperatures among all the indoor units 21 that are turned on. Next, step S44 is executed, that is, to determine whether the highest coil temperature exceeds the sum of the lowest coil temperature and the second temperature difference. In one or more embodiments, the range of the second temperature difference is 5℃-8℃. When the determination result is yes, it indicates that the difference between the highest and lowest coil temperatures is large, and the opening of the indoor unit expansion valve 214 of the indoor unit 21 with the highest coil temperature is further controlled to half of the current opening (i.e., step S45). In other words, the opening of the indoor unit expansion valve 214 of the indoor unit 21 with the highest coil temperature is adjusted twice in a short period of time, and the opening after the two adjustments is only one-quarter of the opening before the initial adjustment. This significantly reduces the amount of refrigerant flowing into the indoor unit 21 with the highest coil temperature, while distributing more refrigerant to other indoor units 21 whose coil temperatures have not exceeded the preset temperature threshold. After step S45 is completed, the control method proceeds to step S5. Additionally, after executing step S44, if the determination result is negative, the control method also proceeds to step S5.

[0037] It should be noted that the parts not mentioned in the second embodiment can be configured the same as in the first embodiment, and will not be repeated here.

[0038] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A control method for a multi-split air conditioning system, characterized in that, The control method includes: When the multi-split air conditioning system is in anti-cold air mode, the indoor unit expansion valve of the indoor unit of the multi-split air conditioning system that receives the start-up signal is fully opened. Detect the coil temperature of each indoor unit that is turned on; The measured coil temperature is compared with a preset temperature threshold, and it is determined whether the coil temperature of all the indoor units that are turned on exceeds the preset temperature threshold. When the judgment result is negative, the indoor unit expansion valve of the indoor unit remains fully open when the coil temperature does not exceed the preset temperature threshold, and the opening of the indoor unit expansion valve of the indoor unit when the coil temperature exceeds the preset temperature threshold is reduced.

2. The control method for a multi-split air conditioning system according to claim 1, characterized in that, When the judgment result is yes, the control method further includes: Control the expansion valve of each indoor unit that is turned on to be fully opened, and control the multi-split air conditioning system to exit the anti-cold air mode.

3. The control method for a multi-split air conditioning system according to claim 1, characterized in that, Before comparing the measured coil temperature with the preset temperature threshold, the control method further includes: The ambient temperature of the indoor unit is detected to determine the preset temperature threshold. The preset temperature threshold is equal to the sum of the difference between the ambient temperature and the first temperature.

4. The control method for a multi-split air conditioning system according to claim 3, characterized in that, The range of the first temperature difference is 10℃-15℃.

5. The control method for a multi-split air conditioning system according to claim 1, characterized in that, The step of reducing the opening of the indoor unit expansion valve of the indoor unit when the coil temperature exceeds the preset temperature threshold includes: Control the opening of the indoor unit expansion valve to half of its current opening.

6. The control method for a multi-split air conditioning system according to claim 5, characterized in that, The control method further includes: Obtain the highest and lowest coil temperatures among all the indoor units that are powered on; Compare the sum of the highest coil temperature, the lowest coil temperature, and the second temperature difference; When the highest coil temperature exceeds the sum value, the opening of the indoor unit expansion valve of the indoor unit with the highest coil temperature is controlled to half of its current opening.

7. The control method for a multi-split air conditioning system according to claim 6, characterized in that, The range of the second temperature difference is 5℃-8℃.

8. The control method for a multi-split air conditioning system according to claim 1, characterized in that, The control method further includes: After a preset time period, the step of detecting the coil temperature of each indoor unit that is turned on is repeated.

9. The control method for a multi-split air conditioning system according to claim 8, characterized in that, The preset time period is in the range of 1 min to 2 min.

10. A multi-split air conditioning system, characterized in that, The control method for a multi-split air conditioning system according to any one of claims 1-9 is executed in the multi-split air conditioning system.

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