Air conditioning system and control method thereof

Abstract

The invention relates to the field of air conditioners, particularly provides an air conditioning system and a control method thereof, and aims to solve the problem that noise is generated when modes of an existing multi-split air conditioner indoor unit are switched. In order to achieve the purpose, the air conditioning system comprises a first four-way valve, a low-pressure main path, a high-pressure main path and an indoor heat exchanger, the second side of the indoor heat exchanger is connected to the high-pressure main path through a high-pressure branch, and the second side of the indoor heat exchanger is connected to the low-pressure main path through a low-pressure branch; the high-pressure valve is arranged on the high-pressure branch; the low-pressure valve is arranged on the low-pressure branch; the control method comprises the following steps that according to the current mode of the air conditioning system, the current mode of a target indoor heat exchanger and a target mode, the working modes of a first four-way valve and a high-pressure valve and a low-pressure valve corresponding to the target indoor heat exchanger are determined; the pressure difference can be balanced, and noise during switching is reduced.

Description

Technical Field

[0001] This invention relates to the field of air conditioning, and specifically provides an air conditioning system and its control method. Background Technology

[0002] With the development of technology, multi-split air conditioners are becoming increasingly widely used, and for better environmental protection, valve boxes are installed at the indoor units. Currently, valve boxes basically adopt a dual-pipe expansion valve mode, that is, expansion valves are installed on both the high-pressure gas pipe and the low-pressure gas pipe for separate control.

[0003] When switching between cooling and heating modes, the indoor unit's gas pipes need to be connected to either the main low-pressure or main high-pressure pipeline via a valve box. During the switch from cooling to heating, the indoor unit's gas pipe pressure is low. After connecting to the main high-pressure pipeline, a high-speed airflow is formed under the influence of the large pressure difference. During the valve switching process, there will inevitably be moments when the valve opening is small. The high-speed airflow passing through the narrowed orifice generates significant refrigerant noise. The switch from heating to cooling is similar.

[0004] Currently, common methods for suppressing refrigerant flow noise include: 1. Source treatment: reducing valve noise through slotted, tortuous channel, and multi-hole valve structures. However, this method is not feasible when the valve is fixed or due to cost constraints. 2. Reducing valve noise through sound-absorbing materials. This method still increases costs, and installation may be limited by size. 3. Phased valve control: during switching, the valve is first opened at a low degree to balance the pressure difference before opening to the maximum. When the valve opening is very low, the resulting impedance is high, the airflow velocity is low, and only a small amount of noise is generated. After the pressure difference is balanced, the valve opening is increased. At this time, the airflow velocity is reduced under low pressure difference, avoiding the generation of high-decibel noise. However, the effectiveness of this solution varies greatly for valves with different performance characteristics. Even with the same method, some valves require a very low opening to achieve low-decibel noise, where the effect of balancing the pressure difference is extremely limited.

[0005] Therefore, there is an urgent need in this field for an air conditioning system and its control method to solve the above-mentioned technical problems. Summary of the Invention

[0006] The present invention aims to solve the above-mentioned technical problem, namely, to solve the problem of noise generated when the indoor unit of a multi-split air conditioner switches modes.

[0007] In a first aspect, the present invention provides a control method for an air conditioning system, the air conditioning system comprising a first four-way valve, a low-pressure main line, a high-pressure main line, and an indoor heat exchanger, wherein the high-pressure main line is connected to a second port of the first four-way valve, the low-pressure main line is connected to a third port and a fourth port of the first four-way valve, a second side of the indoor heat exchanger is connected to the high-pressure main line via a high-pressure branch line, and the second side of the indoor heat exchanger is connected to the low-pressure main line via a low-pressure branch line.

[0008] The air conditioning system also includes:

[0009] A high-pressure valve is installed on the high-pressure branch line;

[0010] A low-pressure valve is installed on the low-pressure branch;

[0011] The control method includes the following steps:

[0012] Based on the current mode of the air conditioning system, the current mode of the target indoor heat exchanger, and the target mode, determine the operating modes of the first four-way valve and the corresponding high-pressure valve and low-pressure valve of the target indoor heat exchanger.

[0013] In a specific implementation of the control method for the aforementioned air conditioning system, "determining the operating modes of the first four-way valve and the high-pressure valve and low-pressure valve corresponding to the target indoor heat exchanger based on the current mode of the air conditioning system, the current mode of the target indoor heat exchanger, and the target mode" includes:

[0014] In full cooling mode, when the indoor heat exchanger switches from cooling or cooling standby to heating mode, the low-pressure valve is closed, the high-pressure valve is opened, and then the first four-way valve is switched.

[0015] In a specific implementation of the control method for the aforementioned air conditioning system, "determining the operating modes of the first four-way valve and the high-pressure valve and low-pressure valve corresponding to the target indoor heat exchanger based on the current mode of the air conditioning system, the current mode of the target indoor heat exchanger, and the target mode" further includes:

[0016] In the main cooling mode, when the indoor heat exchanger switches from heating or heating standby mode to cooling mode, and then switches to full cooling mode, it first controls the high-pressure main circuit to disconnect. After a first preset time, it opens the low-pressure valve and closes the high-pressure valve.

[0017] In a specific implementation of the control method for the aforementioned air conditioning system, the air conditioning system further includes a main liquid pipe, and the first side of the indoor heat exchanger is connected to the main liquid pipe via a branch liquid pipe. A throttling element is provided on the branch liquid pipe. The method of "determining the operating modes of the first four-way valve and the corresponding high-pressure valve and low-pressure valve of the target indoor heat exchanger based on the current mode of the air conditioning system, the current mode of the target indoor heat exchanger, and the target mode" further includes:

[0018] When the indoor heat exchanger switches from cooling or cooling standby mode to heating mode in main cooling or main heating mode, the low-pressure valve is closed, the high-pressure valve is opened to a preset degree or closed, the throttling element is opened to the maximum degree, and after waiting for a second preset time, the low-pressure valve is closed and the high-pressure valve is opened.

[0019] In a specific implementation of the control method for the aforementioned air conditioning system, "determining the operating modes of the first four-way valve and the high-pressure valve and low-pressure valve corresponding to the target indoor heat exchanger based on the current mode of the air conditioning system, the current mode of the target indoor heat exchanger, and the target mode" further includes:

[0020] In the main cooling mode, when the indoor heat exchanger switches from heating mode or heating standby mode to cooling mode, the low-pressure valve opens to a preset opening degree, the high-pressure valve closes, the throttling element closes, and after waiting for a third preset time, the low-pressure valve is controlled to open and the high-pressure valve is closed.

[0021] In a specific implementation of the control method for the aforementioned air conditioning system, "determining the operating modes of the first four-way valve and the high-pressure valve and low-pressure valve corresponding to the target indoor heat exchanger based on the current mode of the air conditioning system, the current mode of the target indoor heat exchanger, and the target mode" further includes:

[0022] In the main cooling mode, when the indoor heat exchanger switches from heating mode or heating standby mode to cooling mode, the high-pressure main circuit is cut off. After a fourth preset time, the high-pressure valve is closed, and then the low-pressure valve is opened. After closing the high-pressure valve and before opening the low-pressure valve, the refrigerant flow in the high-pressure main circuit is restored.

[0023] In a specific implementation of the control method for the aforementioned air conditioning system, "determining the operating modes of the first four-way valve and the high-pressure valve and low-pressure valve corresponding to the target indoor heat exchanger based on the current mode of the air conditioning system, the current mode of the target indoor heat exchanger, and the target mode" further includes:

[0024] In the main heating mode, when the indoor heat exchanger switches from heating mode or heating standby mode to cooling mode, the low-pressure valve opens to a preset opening degree, the high-pressure valve closes, the throttling element is then closed, and after waiting for a third preset time period, the low-pressure valve is controlled to open and the high-pressure valve is closed.

[0025] In a specific implementation of the control method for the aforementioned air conditioning system, "determining the operating modes of the first four-way valve and the high-pressure valve and low-pressure valve corresponding to the target indoor heat exchanger based on the current mode of the air conditioning system, the current mode of the target indoor heat exchanger, and the target mode" further includes:

[0026] In the main heating mode, when the indoor heat exchanger switches from heating mode or heating standby mode to cooling mode; the first four-way valve is controlled to close, and after a fifth preset time, the high-pressure valve is closed, and then the low-pressure valve is opened. After the high-pressure valve is closed, but before the low-pressure valve is opened, the first four-way valve is opened.

[0027] In a specific implementation of the control method for the aforementioned air conditioning system, "determining the operating modes of the first four-way valve and the high-pressure valve and low-pressure valve corresponding to the target indoor heat exchanger based on the current mode of the air conditioning system, the current mode of the target indoor heat exchanger, and the target mode" further includes:

[0028] In defrost mode or heating oil return mode, the high-pressure main circuit is cut off. After waiting for a sixth preset time, all low-pressure valves are opened and the high-pressure valves are closed. After the defrost mode or heating oil return mode ends, the low-pressure valves and the high-pressure valves return to their initial state.

[0029] In a specific implementation of the control method for the above-mentioned air conditioning system, the air conditioning system further includes a main liquid pipe and a first electronic expansion valve. The first side of the indoor heat exchanger is connected to the main liquid pipe via a branch liquid pipe, and the first electronic expansion valve is connected to the branch liquid pipe and the low-pressure branch.

[0030] In a specific embodiment of the control method for the above-mentioned air conditioning system, the control method includes:

[0031] Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger, determine the operating modes of the high-pressure valve, the low-pressure valve, the first electronic expansion valve and the first four-way valve corresponding to the target indoor heat exchanger.

[0032] In a specific implementation of the control method for the aforementioned air conditioning system, a throttling element is provided on the liquid pipe branch, and the throttling element is located between the first electronic expansion valve and the indoor heat exchanger. "Determining the operating modes of the high-pressure valve, low-pressure valve, first electronic expansion valve, and first four-way valve corresponding to the target indoor heat exchanger based on the current mode of the air conditioning system, the current mode of the target indoor heat exchanger, and the target mode" includes:

[0033] In the main cooling mode, when the indoor heat exchanger switches from heating mode or heating standby mode to cooling mode, the low-pressure valve opens to a preset opening degree, the high-pressure valve closes, the first electronic expansion valve opens to its maximum opening degree, then the throttling element closes, and after waiting for a third preset time period, the low-pressure valve is controlled to open and the high-pressure valve closes.

[0034] In a specific implementation of the control method for the aforementioned air conditioning system, a throttling element is provided on the liquid pipe branch, and the throttling element is located between the first electronic expansion valve and the indoor heat exchanger. "Determining the operating modes of the high-pressure valve, low-pressure valve, first electronic expansion valve, and first four-way valve corresponding to the target indoor heat exchanger based on the current mode of the air conditioning system, the current mode of the target indoor heat exchanger, and the target mode" includes:

[0035] In the main heating mode, when the indoor heat exchanger switches from heating mode or heating standby mode to cooling mode, the low-pressure valve opens to a preset opening degree, the high-pressure valve closes, the first electronic expansion valve opens to its maximum opening degree, then the throttling element closes, and after waiting for a third preset time period, the low-pressure valve is controlled to open and the high-pressure valve closes.

[0036] In a specific implementation of the control method for the above-mentioned air conditioning system, the high-pressure valve and the low-pressure valve are integrated into a three-way valve. The first port of the three-way valve is connected to the indoor heat exchanger, the second port is connected to the high-pressure branch, and the third port is connected to the low-pressure branch.

[0037] In a second aspect, the present invention provides an air conditioning system including a control module configured to execute the control method of the air conditioning system as described above.

[0038] When adopting the above technical solution, the control method of the present invention includes the following steps:

[0039] Based on the current mode of the air conditioning system, the current mode of the target indoor heat exchanger, and the target mode, the operating modes of the first four-way valve and the corresponding high-pressure and low-pressure valves of the target indoor heat exchanger are determined. By adjusting the operating modes, the pressure difference between the high-pressure and low-pressure valves can be kept to zero or minimal, ensuring minimal noise during mode switching of the indoor heat exchanger and maintaining indoor comfort.

[0040] Moreover, this method does not involve external equipment; it relies solely on the valves of the air conditioning system for control, thus saving costs and expanding its application scenarios. Furthermore, by switching valve modes, it goes beyond simply opening slightly and then increasing the opening; even when using this control method with valves of varying performance characteristics, it does not generate significant noise, ensuring indoor comfort. Attached Figure Description

[0041] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0042] Figure 1 This is a schematic diagram of the air conditioning system provided in Embodiment 1 of the present invention;

[0043] Figure 2 This is a flowchart of the control method for the air conditioning system provided in Embodiments 1 and 3 of the present invention;

[0044] Figure 3 This is a schematic diagram of the air conditioning system provided in Embodiment 2 of the present invention;

[0045] Figure 4 This is a flowchart of the control method for the air conditioning system provided in Embodiments 2 and 4 of the present invention;

[0046] Figure 5 This is a schematic diagram of the air conditioning system provided in Embodiment 3 of the present invention;

[0047] Figure 6 This is a schematic diagram of the air conditioning system provided in Embodiment 4 of the present invention.

[0048] List of reference numerals in the attached diagram:

[0049] 1b. Liquid pipe expansion valve; 1c. Indoor unit electronic expansion valve; 1d. Indoor heat exchanger; 1f. Low-pressure valve; 1g. High-pressure valve; 1h. First electronic expansion valve; 4. Compressor; 5. Oil separator; 6. Gas-liquid separator; 7. Outdoor heat exchanger; 7a. First four-way valve; 7b. Defrost sensor; 7c. Outdoor unit electronic expansion valve; 8a. Second four-way valve; 9. Outdoor fan; 10. Second four-way valve; 11a. Liquid main line; 12a. Low-pressure gas pipe; 13a. High-pressure gas pipe. Detailed Implementation

[0050] 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.

[0051] It should be noted that in the description of this invention, terms such as "upper," "lower," "left," "right," "inner," and "outer," indicating directional or positional relationships, are based on the directional or positional relationships shown in the accompanying drawings. These are merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0052] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, 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.

[0053] To address the noise issue generated when switching modes in existing multi-split air conditioner indoor units, this invention discloses an air conditioning system and its control method.

[0054] Example 1

[0055] like Figure 1 As shown, this embodiment discloses an air conditioning system, which includes an outdoor heat exchanger 7, a first four-way valve 7a, a compressor 4, a low-pressure main line, a high-pressure main line, a liquid main line 11a, an indoor heat exchanger 1d, a low-pressure valve 1f, a high-pressure valve 1g, and a throttling element.

[0056] There are multiple outdoor heat exchangers 7 and the first four-way valve 7a, and they are set up one-to-one to ensure that each outdoor heat exchanger 7 can be controlled individually. Especially during defrosting, defrosting can be performed sequentially without affecting the normal operation of other outdoor heat exchangers 7, so as to ensure the normal operation of the air conditioning system.

[0057] Multiple outdoor heat exchangers 7 are connected in parallel, and multiple first four-way valves 7a are also connected in parallel. The first side of the outdoor heat exchanger 7 is connected to the first port of the first four-way valve 7a, the exhaust port of the compressor 4 is connected to the second port of the first four-way valve 7a, the suction port of the compressor 4 is connected to the low-pressure main circuit, and the second ports of multiple first four-way valves 7a are all connected to the exhaust port of the compressor 4.

[0058] The high-pressure main circuit is connected to the second port of the first four-way valve 7a. Specifically, the air conditioning system also includes a second four-way valve 8a. The exhaust port of the compressor 4 is also connected to the first port of the second four-way valve 8a. The high-pressure main circuit is connected to the second port of the second four-way valve 8a, that is, the high-pressure main circuit is connected to the exhaust port of the compressor 4 through the second four-way valve 8a. Moreover, the first port of the second four-way valve is also connected to the second port of the first four-way valve 7a through a pipeline, that is, the high-pressure pipeline is connected to the second port of the first four-way valve 7a through the first and second ports of the second four-way valve. The third and fourth ports of the second four-way valve 8a are both connected to the low-pressure main circuit. The connection between the first and second ports of the second four-way valve 8a allows high-temperature and high-pressure refrigerant to flow into the high-pressure main circuit. The disconnection between the first and second ports of the second four-way valve 8a can cut off the flow in the high-pressure main circuit. Furthermore, after the first and second ports of the four-way valve are disconnected, the second port will connect to the third port, that is, the high-pressure main circuit will connect to the low-pressure main circuit.

[0059] The low-pressure main line is connected to the third and fourth ports of the first four-way valve 7a. The second side of the outdoor heat exchanger 7 is connected to the liquid main line 11a, specifically through an outdoor branch line. A second electronic expansion valve is installed on the outdoor branch line.

[0060] In full heating mode or main heating mode, the first port of the first four-way valve 7a is disconnected from the second port, and the first port is connected to the third or fourth port; this allows the refrigerant flowing out of the outdoor heat exchanger 7 to flow to the low-pressure main circuit so that it can flow into the compressor 4.

[0061] In full cooling mode or main cooling mode, the first port of the first four-way valve 7a is connected to the second port, and neither the first port nor the second port is connected to the third port or the fourth port; this allows the high-temperature and high-pressure refrigerant to flow into the outdoor heat exchanger 7, and then from the outdoor heat exchanger 7 into the indoor heat exchanger 1d for cooling.

[0062] The first side of the indoor heat exchanger 1d is connected to the main liquid pipe 11a via a liquid pipe branch. A throttling element, specifically an indoor electronic expansion valve, is installed on the liquid pipe branch, located close to the indoor heat exchanger 1d. In addition, a liquid pipe expansion valve 1b is installed on the liquid pipe branch, specifically on the side of the indoor electronic expansion valve away from the indoor heat exchanger 1d.

[0063] The second side of the indoor heat exchanger 1d is connected to the high-pressure main circuit via a high-pressure branch, and the second side of the indoor heat exchanger 1d is connected to the low-pressure main circuit via a low-pressure branch.

[0064] High-pressure valve 1g is located on the high-pressure branch; specifically, it is a high-pressure electronic expansion valve. Low-pressure valve 1f is located on the low-pressure branch; specifically, it is a low-pressure electronic expansion valve. The air conditioning system also includes a control module configured to execute the control methods of the air conditioning system.

[0065] The high-pressure valve 1g, low-pressure valve 1f, and liquid pipe expansion valve 1b are all located inside the valve box and controlled through the valve box, which ensures the stability of the control and better protects the valves.

[0066] like Figure 2 As shown, the control method of this air conditioning system includes the following steps:

[0067] S1. Obtain the current mode of the air conditioning system, the current mode of the target indoor unit, and the target mode;

[0068] S2. Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, determine the working mode of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d.

[0069] The phrase "determining the operating modes of the first four-way valve 7a and the corresponding high-pressure valve 1g and low-pressure valve 1f of the target indoor heat exchanger 1d based on the current mode of the air conditioning system, the current mode of the target indoor heat exchanger 1d, and the target mode" includes:

[0070] In full cooling mode, when indoor heat exchanger 1d switches from cooling or cooling standby to heating mode, the low-pressure valve 1f is closed, the high-pressure valve 1g is opened, and then the first four-way valve 7a is switched. Full cooling mode refers to all indoor units being in cooling mode or cooling standby mode.

[0071] In full cooling mode, the first and second ports of the second four-way valve 8a are disconnected, preventing the flow of high-temperature, high-pressure refrigerant in the high-pressure main circuit. Both the high-pressure main circuit and the high-pressure branch circuit are in a low-pressure state, roughly the same as the pressure in the low-pressure gas pipe 12a. This ensures there is no pressure difference between the two sides of the low-pressure valve 1f and the high-pressure valve 1g. When the high-pressure valve 1g is opened, the lack of pressure difference results in a lower refrigerant flow rate and less noise. After the high-pressure valve 1g is opened, switching the first four-way valve 7a is also possible. Since the high-pressure valve 1g is fully open, the high-temperature, high-pressure refrigerant flowing into the indoor heat exchanger 1d produces less noise due to its larger diameter, thus minimizing noise and ensuring comfort.

[0072] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, the operating modes of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d are determined." This also includes:

[0073] In the main cooling mode, when the indoor heat exchanger 1d switches from heating or heating standby mode to cooling mode, and then to full cooling mode, it first controls the high-pressure main circuit to disconnect. After a first preset time, it opens the low-pressure valve 1f and closes the high-pressure valve 1g. The first preset time is preferably 3 seconds, but in other embodiments it can be 5 seconds, etc. The main cooling mode refers to a situation where some indoor units are in cooling mode or cooling standby mode, while others are in heating mode or heating standby mode; and the number of indoor units in cooling mode or cooling standby mode is relatively large. At this time, the first and second ports of the second four-way valve 8a are connected, and the high-pressure main circuit and high-pressure branch circuit are filled with high-temperature, high-pressure refrigerant.

[0074] First, disconnect the first and second ports of the second four-way valve 8a to cut off the high-pressure main circuit. After waiting for a first preset time, the high-pressure main circuit and high-pressure branch circuit can be connected, allowing the refrigerant in the high-pressure main circuit to flow to the low-pressure main circuit, thus depressurizing the high-pressure main circuit. This ensures that the pressures of the high-pressure and low-pressure main circuits are the same. Simultaneously, the pressure on the second side of the indoor heat exchanger 1d will be the same as that of the low-pressure main circuit. At this time, the pressures on both sides of the low-pressure valve 1f will be kept the same. Since the pressure difference is zero or very small, opening the low-pressure valve 1f will not produce noise, and closing the high-pressure valve 1g will also not produce noise. Even if noise is produced, it will be minimal and will not affect indoor comfort.

[0075] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, the operating modes of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d are determined." This also includes:

[0076] In main cooling or main heating mode, when the indoor heat exchanger 1d switches from cooling or cooling standby mode to heating mode, the low-pressure valve 1f is closed, and the high-pressure valve 1g is opened to a preset degree or closed. The throttling element is opened to its maximum degree. After waiting for a second preset time, the low-pressure valve 1f is closed and the high-pressure valve 1g is opened. The preset opening degree of the high-pressure valve 1g refers to a relatively small opening degree, generally not exceeding one-fifth of the total opening degree.

[0077] In cooling mode or cooling standby mode, the second side of the indoor heat exchanger 1d is under low pressure, meaning there is a large pressure difference across the high-pressure valve 1g. Before switching to heating mode, the pressure on the second side of the indoor heat exchanger 1d needs to be increased. Closing the low-pressure valve 1f and opening the indoor electronic expansion valve to its maximum extent will cause the pressure on the second side of the indoor heat exchanger 1d to rise as the refrigerant flows into the liquid pipe branch, reducing the pressure across the high-pressure valve 1g and minimizing the pressure difference. Opening the high-pressure valve 1g to a smaller opening results in less refrigerant flow, less noise, and a rapid reduction in the pressure difference across the valve. At this point, opening the high-pressure valve 1g again will produce less noise due to the smaller pressure difference.

[0078] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, the operating modes of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d are determined." This also includes:

[0079] In the main cooling mode, when the indoor heat exchanger 1d switches from heating mode or heating standby mode to cooling mode, the low-pressure valve 1f opens to a preset opening degree, the high-pressure valve 1g closes, the throttling element closes, and after a third preset time, the low-pressure valve 1f opens again, and the high-pressure valve 1g closes. Then, the indoor electronic expansion valve is controlled according to the system status. The preset opening degree of the low-pressure valve 1f refers to a small opening degree, generally not exceeding one-fifth of the total opening degree. The third preset time is preferably 50 seconds, but in other embodiments it can also be 40 seconds or 1 minute; as long as the pressure difference on both sides of the low-pressure valve 1f can be balanced.

[0080] In heating mode or heating standby mode, the second side of the indoor heat exchanger 1d uses high-temperature, high-pressure refrigerant, resulting in a large pressure difference across the low-pressure valve 1f. Before opening the low-pressure valve 1f, this pressure difference needs to be reduced. When the low-pressure valve 1f is slightly open, the resistance is high and the airflow velocity is low, but this low opening does not generate significant noise. A slightly open low-pressure valve 1f reduces the pressure difference across it, resulting in less noise when the valve is opened further. Since the system liquid line pressure is generally high, closing the indoor unit's electronic expansion valve 1c further reduces the pressure difference across the low-pressure valve 1f.

[0081] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, the operating modes of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d are determined." This also includes:

[0082] In the main cooling mode, when the indoor heat exchanger 1d switches from heating mode or heating standby mode to cooling mode, the high-pressure main circuit is disconnected (specifically, the first and second ports of the second four-way valve 8a are disconnected, while the second and third ports are connected). After a fourth preset time, the high-pressure valve 1g is closed, and then the low-pressure valve 1f is opened. After closing the high-pressure valve 1g but before opening the low-pressure valve 1f, the refrigerant flow in the high-pressure main circuit is restored. The fourth preset time is preferably 5 seconds, but in other embodiments it can also be 4 seconds, 7 seconds, etc.

[0083] After the high-pressure main line is disconnected, the pressure in both the high-pressure main line and the high-pressure branch line drops rapidly. In this state, the pressure difference across both the high-pressure valve 1g and the low-pressure valve 1f is small. Opening the low-pressure valve 1f does not generate significant noise, ensuring indoor comfort. However, before the high-pressure main line is restored to its normal flow, it will temporarily affect the heating performance of other indoor units.

[0084] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, the operating modes of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d are determined." This also includes:

[0085] In the main heating mode, when the indoor heat exchanger 1d switches from heating mode or heating standby mode to cooling mode, the low-pressure valve 1f opens to a preset opening degree, the high-pressure valve 1g closes, then the throttling element closes, and after waiting for a third preset time, the low-pressure valve 1f is controlled to open and the high-pressure valve 1g is controlled to close.

[0086] In heating mode or heating standby mode, the second side of the indoor heat exchanger 1d uses high-temperature, high-pressure refrigerant, resulting in a large pressure difference across the low-pressure valve 1f. Before opening the low-pressure valve 1f, this pressure difference needs to be reduced. When the low-pressure valve 1f is slightly open, the resistance is high and the airflow velocity is low, but this low opening does not generate significant noise. A slightly open low-pressure valve 1f reduces the pressure difference across it, resulting in less noise when the valve is opened further. Since the system liquid line pressure is generally high, closing the indoor unit's electronic expansion valve 1c further reduces the pressure difference across the low-pressure valve 1f.

[0087] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, the operating modes of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d are determined." This also includes:

[0088] In the main heating mode, when the indoor heat exchanger 1d switches from heating mode or heating standby mode to cooling mode, the first four-way valve 7a is closed. After a fifth preset time, the high-pressure valve 1g is closed, and then the low-pressure valve 1f is opened. After the high-pressure valve 1g is closed but before the low-pressure valve 1f is opened, the first four-way valve 7a is opened. The fifth preset time is preferably 5 seconds, but in other embodiments it can be 4 seconds or 6 seconds, etc.

[0089] The first four-way valve 7a being closed means that the first and second ports of the first four-way valve 7a are connected, and neither the first nor the second port is connected to the third or fourth port. This allows the pressure of the entire air conditioning system to drop rapidly, reducing the pressure on the second side of the indoor heat exchanger 1d, and minimizing the pressure difference between the low-pressure valve 1f and the high-pressure valve 1g. Opening the low-pressure valve 1f will not generate significant noise. The first four-way valve 7a being open means that the first port of the first four-way valve 7a is disconnected from the second port, and the first port is connected to the third or fourth port.

[0090] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, the operating modes of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d are determined." This also includes:

[0091] In defrost mode or heating oil return mode, the high-pressure main circuit is disconnected (specifically, the first and second ports of the second four-way valve 8a are disconnected, while the second and third ports are connected). After a sixth preset time, all low-pressure valves 1f open and high-pressure valves 1g close. After the defrost mode or heating oil return mode ends, low-pressure valves 1f and high-pressure valves 1g return to their initial state. The sixth preset time is specifically 5 seconds, but in other embodiments it can also be 4 seconds or 6 seconds, etc.

[0092] The high-pressure main line is disconnected and connected to the low-pressure main line, which can rapidly reduce the pressure in both the high-pressure main line and the high-pressure branch line. After a preset time period, the pressure in the high-pressure main line can be reduced to the same level as that in the low-pressure main line, resulting in a small or no pressure difference between the low-pressure valve 1f and the high-pressure valve 1g. Opening the low-pressure valve 1f will not generate significant noise.

[0093] Example 2

[0094] like Figure 3 As shown, this embodiment discloses an air conditioning system. The structure of the air conditioning system is basically the same as that of Embodiment 1, except that the air conditioning system also includes a first electronic expansion valve 1h, which is connected to the liquid pipe branch and the low-pressure branch. Moreover, the first electronic expansion valve 1h is located in the valve box. Specifically, the first electronic expansion valve 1h and the expansion valve matched with the subcooling heat exchanger in the valve box are one and the same, and it is only used as the first electronic expansion valve 1h during defrosting. In other situations, it is used in conjunction with the subcooling heat exchanger in the valve box.

[0095] like Figure 4 As shown, the control method of this air conditioning system includes:

[0096] S1. Obtain the current mode of the air conditioning system, the current mode of the target indoor unit, and the target mode;

[0097] S2. Based on the current mode of the air conditioning system, the current mode and target mode of the target indoor heat exchanger 1d, determine the working modes of the high-pressure valve 1g, low-pressure valve 1f, first electronic expansion valve 1h and first four-way valve 7a corresponding to the target indoor heat exchanger 1d.

[0098] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, determine the operating modes of the high-pressure valve 1g, low-pressure valve 1f, first electronic expansion valve 1h, and first four-way valve 7a corresponding to the target indoor heat exchanger 1d" including:

[0099] In the main cooling mode, when the indoor heat exchanger 1d switches from heating mode or heating standby mode to cooling mode, the low-pressure valve 1f opens to a preset opening degree, the high-pressure valve 1g closes, the first electronic expansion valve 1h opens to its maximum opening degree, then the throttling element closes, and after waiting for a third preset time, the low-pressure valve 1f is controlled to open and the high-pressure valve 1g is closed.

[0100] In heating mode or heating standby mode, the second side of the indoor heat exchanger 1d uses high-temperature, high-pressure refrigerant, resulting in a large pressure difference across the low-pressure valve 1f. Before opening the low-pressure valve 1f, this pressure difference needs to be reduced. When the low-pressure valve 1f is slightly open, the resistance is high and the airflow velocity is low, but this low opening does not generate significant noise. The slight opening of the low-pressure valve 1f reduces the pressure difference across it, resulting in less noise when it is opened later. Since the system liquid line pressure is generally high, closing the indoor unit's electronic expansion valve 1c and using the first electronic expansion valve 1h to increase the pressure in the low-pressure branch further reduces the pressure difference across the low-pressure valve 1f, thus minimizing noise when it is opened later.

[0101] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, determine the operating modes of the high-pressure valve 1g, low-pressure valve 1f, first electronic expansion valve 1h, and first four-way valve 7a corresponding to the target indoor heat exchanger 1d" including:

[0102] In the main heating mode, when the indoor heat exchanger 1d switches from heating mode or heating standby mode to cooling mode, the low-pressure valve 1f opens to a preset opening degree, the high-pressure valve 1g closes, the first electronic expansion valve 1h opens to its maximum opening degree, then the throttling element closes, and after waiting for a third preset time, the low-pressure valve 1f is controlled to open and the high-pressure valve 1g is controlled to close.

[0103] In heating mode or heating standby mode, the second side of the indoor heat exchanger 1d uses high-temperature, high-pressure refrigerant, resulting in a large pressure difference across the low-pressure valve 1f. Before opening the low-pressure valve 1f, this pressure difference needs to be reduced. When the low-pressure valve 1f is slightly open, the resistance is high and the airflow velocity is low, but this low opening does not generate significant noise. The slight opening of the low-pressure valve 1f reduces the pressure difference across it, resulting in less noise when opening it. Since the system liquid line pressure is generally high, closing the indoor unit's electronic expansion valve 1c and using the first electronic expansion valve 1h to increase the pressure in the low-pressure branch further reduces the pressure difference across the low-pressure valve 1f, thus minimizing noise when opening it.

[0104] Example 3

[0105] like Figure 5 As shown, this embodiment discloses an air conditioning system, which has a structure that is basically the same as the air conditioning system in Embodiment 1. The difference is that the high-pressure valve 1g and the low-pressure valve 1f are integrated into a three-way valve. The first port of the three-way valve is connected to the indoor heat exchanger 1d, the second port is connected to the high-pressure branch, and the third port is connected to the low-pressure branch.

[0106] In a three-way valve, an opening of 0% means that the first and third ports are connected, but the first port is not connected to the second port. A half-open state means that the first port is not connected to either the second or third port, i.e., the indoor heat exchanger 1d is disconnected from both the low-pressure and high-pressure branches. A fully open state means that the first and second ports are connected, but the third port is not connected. A slightly lower half-open state means that the opening between the first and third ports is small, generally not exceeding one-fifth of the total opening. A slightly higher half-open state means that the opening between the first and second ports is small, generally not exceeding one-fifth of the total opening.

[0107] The two sides of the three-way valve refer to the indoor heat exchanger 1d side and the branch side of the three-way valve.

[0108] like Figure 2 As shown, the control method of this air conditioning system includes the following steps:

[0109] S1. Obtain the current mode of the air conditioning system, the current mode of the target indoor unit, and the target mode;

[0110] S2. Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, determine the working mode of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d.

[0111] The phrase "determining the operating modes of the first four-way valve 7a and the corresponding high-pressure valve 1g and low-pressure valve 1f of the target indoor heat exchanger 1d based on the current mode of the air conditioning system, the current mode of the target indoor heat exchanger 1d, and the target mode" includes:

[0112] In full cooling mode, when indoor heat exchanger 1d switches from cooling or cooling standby to heating mode, the three-way valve opens from 0 to fully open, and then the first four-way valve 7a switches. Full cooling mode means that all indoor units are in cooling mode or cooling standby mode.

[0113] In full cooling mode, the first and second ports of the second four-way valve 8a are disconnected, preventing the flow of high-temperature, high-pressure refrigerant in the high-pressure main circuit. Both the high-pressure main circuit and the high-pressure branch circuit are in a low-pressure state, approximately the same as the pressure in the low-pressure gas pipe 12a. This eliminates the pressure difference across the three-way valve. When the high-pressure valve 1g is opened, the lack of pressure difference results in a lower refrigerant flow rate and less noise. After the three-way valve is fully open, switching to the first four-way valve 7a, with both ports fully open, allows the high-temperature, high-pressure refrigerant to flow into the indoor heat exchanger 1d. Due to the larger diameter of the inlet, this process generates less noise and does not significantly impact comfort.

[0114] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, the operating modes of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d are determined." This also includes:

[0115] In the main cooling mode, when the indoor heat exchanger 1d switches from heating or heating standby mode to cooling mode, and then to full cooling mode, the high-pressure main circuit is cut off first. After a first preset time, the three-way valve changes from fully open to 0 degree. The first preset time is preferably 3 seconds, but in other embodiments it can be 5 seconds, etc. The main cooling mode refers to a situation where some indoor units are in cooling mode or cooling standby mode, while others are in heating mode or heating standby mode; and the number of indoor units in cooling mode or cooling standby mode is relatively large. At this time, the first and second ports of the second four-way valve 8a are connected, and the high-pressure main circuit and high-pressure branch circuit are filled with high-temperature, high-pressure refrigerant.

[0116] First, disconnect the first and second ports of the second four-way valve 8a to cut off the high-pressure main circuit. After waiting for a first preset time, the high-pressure main circuit and high-pressure branch circuit can be connected, allowing the refrigerant in the high-pressure main circuit to flow to the low-pressure main circuit, thus depressurizing the high-pressure main circuit and maintaining the pressure of the high-pressure main circuit and the low-pressure main circuit at the same level. At the same time, the pressure on the second side of the indoor heat exchanger 1d will be the same as that of the low-pressure main circuit. At this time, the pressure on both sides of the three-way valve can be kept the same. Since the pressure difference is zero or very small, no noise will be generated when switching the three-way valve. Even if noise is generated, it will be small and will not affect the comfort of the room.

[0117] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, the operating modes of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d are determined." This also includes:

[0118] In main cooling or main heating mode, when indoor heat exchanger 1d switches from cooling or cooling standby mode to heating mode, the three-way valve switches to a half-open or slightly higher half-open state, the throttling element opens to its maximum degree, and after waiting for a second preset time, the three-way valve switches to a fully open state. In cooling or cooling standby mode, the second side of indoor heat exchanger 1d is under low pressure, meaning the pressure difference between the high-pressure branch of the three-way valve and the two sides of indoor heat exchanger 1d is large. Before switching to heating mode, the pressure on the second side of indoor heat exchanger 1d needs to be increased. Disconnecting the first and third ports of the three-way valve and opening the indoor electronic expansion valve to its maximum degree will cause the pressure on the second side of indoor heat exchanger 1d to rise as the refrigerant flows into the liquid pipe branch, reducing the pressure on both sides of high-pressure valve 1g and minimizing the pressure difference. The slightly higher half-open position of the three-way valve results in less refrigerant flow, less noise, and a rapid reduction in the pressure difference between the first and second ports of the three-way valve. At this point, switching the three-way valve to the fully open position will result in less noise due to the smaller pressure difference.

[0119] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, the operating modes of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d are determined." This also includes:

[0120] In the main cooling mode, when the indoor heat exchanger 1d switches from heating mode or heating standby mode to cooling mode, the three-way valve switches to a slightly open position, then closes the throttling element, and waits for a third preset time before controlling the three-way valve to switch to an open position of 0. Afterwards, the indoor electronic expansion valve is controlled according to the system status. The third preset time is preferably 50 seconds, but in other embodiments it can also be 40 seconds or 1 minute; as long as the pressure difference between the first and third ports of the three-way valve can be balanced.

[0121] In heating mode or heating standby mode, the second side of the indoor heat exchanger 1d uses high-temperature, high-pressure refrigerant. The pressure difference between the first and third ports of the three-way valve is significant. Before switching the three-way valve to 0 degree of opening, this pressure difference needs to be reduced. When the three-way valve is in a slightly open position, the resistance is high, the airflow velocity is low, and the low opening does not generate significant noise. Maintaining the three-way valve in a slightly open position reduces the pressure difference between the first and third ports, thus minimizing the noise generated when switching to 0 degree of opening. Since the system liquid line pressure is generally high, closing the indoor unit's electronic expansion valve 1c reduces the pressure difference between the first and third ports of the three-way valve.

[0122] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, the operating modes of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d are determined." This also includes:

[0123] In the main cooling mode, when the indoor heat exchanger 1d switches from heating mode or heating standby mode to cooling mode, the high-pressure main circuit is disconnected (specifically, the first and second ports of the second four-way valve 8a are disconnected, while the second and third ports are connected). After a fourth preset time, the opening of the three-way valve is switched to 0 degrees, and at half opening, the refrigerant flow in the high-pressure main circuit is restored. The fourth preset time is preferably 5 seconds, but in other embodiments it can also be 4 seconds, 7 seconds, etc.

[0124] After the high-pressure main line is disconnected, the pressure in both the high-pressure main line and the high-pressure branch line drops rapidly. In this state, the pressure difference across the three-way valve is small. Opening the three-way valve to 0 degrees will not produce significant noise, ensuring indoor comfort. However, before the high-pressure main line is restored to its normal flow, it will temporarily affect the heating performance of other indoor units.

[0125] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, the operating modes of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d are determined." This also includes:

[0126] In the main heating mode, when the indoor heat exchanger 1d switches from heating mode or heating standby mode to cooling mode, the three-way valve is switched to a slightly lower opening degree, then the throttling element is closed, and after waiting for the third preset time, the three-way valve is controlled to switch to 0 opening degree.

[0127] In heating mode or heating standby mode, the second side of the indoor heat exchanger 1d uses high-temperature, high-pressure refrigerant. The pressure difference between the first and third ports of the three-way valve is relatively large. Before switching to 0 opening, it is necessary to reduce the pressure difference between the first and third ports of the three-way valve. When the valve is half-open (slightly lower opening), the resistance is high, the airflow velocity is low, and no significant noise is generated. Half-opening (slightly lower opening) can reduce the pressure difference across the low-pressure valve 1f, and then switching to 0 opening will generate less noise. Since the system liquid line pressure is generally high, closing the indoor unit's electronic expansion valve 1c can reduce the pressure difference between the first and third ports.

[0128] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, the operating modes of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d are determined." This also includes:

[0129] In the main heating mode, when the indoor heat exchanger 1d switches from heating mode or heating standby mode to cooling mode, the first four-way valve 7a is closed. After a fifth preset time, the three-way valve is switched to 0 degree of opening, and when it is half-open, the first four-way valve 7a is opened. The fifth preset time is preferably 5 seconds, but in other embodiments it can also be 4 seconds or 6 seconds, etc.

[0130] The first four-way valve 7a being closed means that the first and second ports of the first four-way valve 7a are connected, and neither the first nor the second port is connected to the third or fourth port. This allows the pressure of the entire air conditioning system to drop rapidly, reducing the pressure on the second side of the indoor heat exchanger 1d, resulting in a smaller pressure difference across the three-way valve. When switching to 0 opening, it does not generate significant noise. The first four-way valve 7a being open means that the first and second ports of the first four-way valve 7a are disconnected, and the first port is connected to the third or fourth port.

[0131] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, the operating modes of the first four-way valve 7a and the high-pressure valve 1g and low-pressure valve 1f corresponding to the target indoor heat exchanger 1d are determined." This also includes:

[0132] In defrost mode or heating oil return mode, the high-pressure main circuit is cut off (specifically, the first and second ports of the second four-way valve 8a are disconnected, while the second and third ports are connected). After a sixth preset time, all three-way valves of indoor heat exchangers 1d are switched to 0 opening. After the defrost mode or heating oil return mode ends, the three-way valves return to their initial state. The sixth preset time is specifically 5 seconds, but in other embodiments it can also be 4 seconds or 6 seconds, etc.

[0133] When the high-pressure main line is disconnected and connected to the low-pressure main line, the pressure in both the high-pressure main line and the high-pressure branch line drops rapidly. After a preset time period, the pressure in the high-pressure main line drops to the same level as the low-pressure main line, resulting in a small or no pressure difference in the three-way valve. The three-way valve does not generate significant noise when switching to 0 degrees of opening.

[0134] Example 4

[0135] like Figure 6 As shown, this embodiment discloses an air conditioning system. The structure of the air conditioning system is basically the same as that of Embodiment 3, except that the air conditioning system also includes a first electronic expansion valve 1h, which is connected to the liquid pipe branch and the low-pressure branch. Moreover, the first electronic expansion valve 1h is located in the valve box. Specifically, the first electronic expansion valve 1h and the expansion valve matched with the subcooling heat exchanger in the valve box are one, and it is only used as the first electronic expansion valve 1h during defrosting. In other situations, it is used in conjunction with the subcooling heat exchanger in the valve box.

[0136] like Figure 4 As shown, the control method of this air conditioning system includes:

[0137] S1. Obtain the current mode of the air conditioning system, the current mode of the target indoor unit, and the target mode;

[0138] S2. Based on the current mode of the air conditioning system, the current mode and target mode of the target indoor heat exchanger 1d, determine the working modes of the high-pressure valve 1g, low-pressure valve 1f, first electronic expansion valve 1h and first four-way valve 7a corresponding to the target indoor heat exchanger 1d.

[0139] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, determine the operating modes of the high-pressure valve 1g, low-pressure valve 1f, first electronic expansion valve 1h, and first four-way valve 7a corresponding to the target indoor heat exchanger 1d" including:

[0140] In the main cooling mode, when the indoor heat exchanger 1d switches from heating mode or heating standby mode to cooling mode, the three-way valve switches to a slightly lower opening, the first electronic expansion valve 1h opens to its maximum, then the throttling element closes, and after waiting for a third preset time, the three-way valve is controlled to switch to 0 opening.

[0141] In heating mode or heating standby mode, the second side of the indoor heat exchanger 1d uses high-temperature, high-pressure refrigerant. The pressure difference between the first and third ports of the three-way valve is relatively large. Before switching to 9 degrees of opening, it is necessary to reduce the pressure difference between the first and third ports. When the valve is half-open or slightly lower, the resistance is high and the airflow velocity is low, but the low opening does not produce much noise. The low opening can reduce the pressure difference between the first and third ports, and the noise generated when switching to 0 degrees is also relatively small. Since the system liquid line pressure is generally high, closing the indoor unit's electronic expansion valve 1c and allowing the first electronic expansion valve 1h to increase the pressure in the low-pressure branch will reduce the pressure difference between the first and third ports, and the noise generated when switching to 0 degrees will not be significant.

[0142] "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger 1d, determine the operating modes of the high-pressure valve 1g, low-pressure valve 1f, first electronic expansion valve 1h, and first four-way valve 7a corresponding to the target indoor heat exchanger 1d" including:

[0143] In the main heating mode, when the indoor heat exchanger 1d switches from heating mode or heating standby mode to cooling mode, the three-way valve switches to a slightly lower opening, the first electronic expansion valve 1h opens to its maximum, then the throttling element closes, and after waiting for a third preset time, the three-way valve switches to 0 opening.

[0144] In heating mode or heating standby mode, the second side of the indoor heat exchanger 1d uses high-temperature, high-pressure refrigerant. The pressure difference between the first and third interfaces is relatively large, and it is necessary to reduce the pressure difference between the first and third interfaces before switching to 0 opening. At a slightly lower opening, the resistance is high and the airflow velocity is low, but the low opening does not generate significant noise. The low opening reduces the pressure difference between the first and third interfaces, resulting in less noise when switching to 0 opening. Since the system liquid line pressure is generally high, closing the indoor unit's electronic expansion valve 1c and allowing the first electronic expansion valve 1h to increase the pressure in the low-pressure branch reduces the pressure difference between the first and third interfaces, thus minimizing noise when switching to 0 opening.

[0145] 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 an air conditioning system, the air conditioning system comprising a first four-way valve (7a), a low-pressure main line, a high-pressure main line, and an indoor heat exchanger (1d), wherein the high-pressure main line is connected to a second port of the first four-way valve (7a), the low-pressure main line is connected to a third port and a fourth port of the first four-way valve (7a), the second side of the indoor heat exchanger (1d) is connected to the high-pressure main line via a high-pressure branch line, and the second side of the indoor heat exchanger (1d) is connected to the low-pressure main line via a low-pressure branch line; Its features are, The air conditioning system also includes: A high-pressure valve (1g) is installed on the high-pressure branch line; A low-pressure valve (1f) is provided on the low-pressure branch; The control method includes the following steps: Based on the current mode of the air conditioning system, the current mode and target mode of the target indoor heat exchanger (1d), determine the working mode of the first four-way valve (7a) and the high-pressure valve (1g) and low-pressure valve (1f) corresponding to the target indoor heat exchanger (1d).

2. The control method for the air conditioning system according to claim 1, characterized in that, "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger (1d), determine the operating modes of the first four-way valve (7a) and the high-pressure valve (1g) and low-pressure valve (1f) corresponding to the target indoor heat exchanger (1d)" includes: In full cooling mode, when the indoor heat exchanger (1d) switches from cooling or cooling standby to heating mode, the low-pressure valve (1f) is closed, the high-pressure valve (1g) is opened, and then the first four-way valve (7a) is switched.

3. The control method for the air conditioning system according to claim 1, characterized in that, "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger (1d), the operating modes of the first four-way valve (7a) and the high-pressure valve (1g) and low-pressure valve (1f) corresponding to the target indoor heat exchanger (1d) are determined" further includes: In the main cooling mode, when the indoor heat exchanger (1d) switches from heating or heating standby mode to cooling mode, and then switches to full cooling mode, it first controls the high-pressure main circuit to disconnect. After a first preset time, it opens the low-pressure valve (1f) and closes the high-pressure valve (1g).

4. The control method for an air conditioning system according to claim 1, characterized in that, The air conditioning system also includes a main liquid pipe (11a), and the first side of the indoor heat exchanger (1d) is connected to the main liquid pipe (11a) via a branch liquid pipe. A throttling element is provided on the branch liquid pipe. "Determining the operating modes of the first four-way valve (7a) and the high-pressure valve (1g) and low-pressure valve (1f) corresponding to the target indoor heat exchanger (1d) according to the current mode of the air conditioning system, the current mode of the target indoor heat exchanger (1d), and the target mode" also includes: When the indoor heat exchanger (1d) switches from cooling or cooling standby mode to heating mode in the main cooling or main heating mode, the low-pressure valve (1f) is closed, the high-pressure valve (1g) is opened to a preset degree or closed, the throttling element is opened to the maximum degree, and after waiting for a second preset time, the low-pressure valve (1f) is closed and the high-pressure valve (1g) is opened.

5. The control method for the air conditioning system according to claim 4, characterized in that, "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger (1d), the operating modes of the first four-way valve (7a) and the high-pressure valve (1g) and low-pressure valve (1f) corresponding to the target indoor heat exchanger (1d) are determined" further includes: In the main cooling mode, when the indoor heat exchanger (1d) switches from heating mode or heating standby mode to cooling mode, the low-pressure valve (1f) opens to a preset opening degree, the high-pressure valve (1g) closes, the throttling element is then closed, and after waiting for a third preset time, the low-pressure valve (1f) is controlled to open and the high-pressure valve (1g) is closed.

6. The control method for the air conditioning system according to claim 4, characterized in that, "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger (1d), the operating modes of the first four-way valve (7a) and the high-pressure valve (1g) and low-pressure valve (1f) corresponding to the target indoor heat exchanger (1d) are determined" further includes: In the main cooling mode, when the indoor heat exchanger (1d) switches from heating mode or heating standby mode to cooling mode, the high-pressure main circuit is cut off. After a fourth preset time, the high-pressure valve (1g) is closed, and then the low-pressure valve (1f) is opened. After the high-pressure valve (1g) is closed, but before the low-pressure valve (1f) is opened, the refrigerant flow in the high-pressure main circuit is restored.

7. The control method for an air conditioning system according to claim 4, characterized in that, "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger (1d), the operating modes of the first four-way valve (7a) and the high-pressure valve (1g) and low-pressure valve (1f) corresponding to the target indoor heat exchanger (1d) are determined" further includes: In the main heating mode, when the indoor heat exchanger (1d) switches from heating mode or heating standby mode to cooling mode, the low-pressure valve (1f) opens to a preset opening degree, the high-pressure valve (1g) closes, the throttling element is then closed, and after waiting for a third preset time, the low-pressure valve (1f) is controlled to open and the high-pressure valve (1g) is closed.

8. The control method for an air conditioning system according to claim 1, characterized in that, "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger (1d), the operating modes of the first four-way valve (7a) and the high-pressure valve (1g) and low-pressure valve (1f) corresponding to the target indoor heat exchanger (1d) are determined" further includes: When the indoor heat exchanger (1d) switches from heating mode or heating standby mode to cooling mode in the main heating mode, the first four-way valve (7a) is closed. After a fifth preset time, the high-pressure valve (1g) is closed, and then the low-pressure valve (1f) is opened. After the high-pressure valve (1g) is closed, but before the low-pressure valve (1f) is opened, the first four-way valve (7a) is opened.

9. The control method for an air conditioning system according to claim 1, characterized in that, "Based on the current mode of the air conditioning system, the current mode and the target mode of the target indoor heat exchanger (1d), the operating modes of the first four-way valve (7a) and the high-pressure valve (1g) and low-pressure valve (1f) corresponding to the target indoor heat exchanger (1d) are determined" further includes: In defrost mode or heating oil return mode, the high-pressure main circuit is cut off. After waiting for a sixth preset time, all low-pressure valves (1f) are opened and the high-pressure valve (1g) is closed. After the defrost mode or heating oil return mode ends, the low-pressure valve (1f) and the high-pressure valve (1g) are restored to their initial state.

10. The control method for an air conditioning system according to claim 1, characterized in that, The air conditioning system also includes a main liquid pipe (11a) and a first electronic expansion valve (1h). The first side of the indoor heat exchanger (1d) is connected to the main liquid pipe (11a) via a branch liquid pipe. The first electronic expansion valve (1h) is connected to the branch liquid pipe and the low-pressure branch.

11. The control method for an air conditioning system according to claim 10, characterized in that, The control method includes: Based on the current mode of the air conditioning system, the current mode and target mode of the target indoor heat exchanger (1d), determine the operating modes of the high-pressure valve (1g), the low-pressure valve (1f), the first electronic expansion valve (1h), and the first four-way valve (7a) corresponding to the target indoor heat exchanger (1d).

12. The control method for an air conditioning system according to claim 11, characterized in that, A throttling element is provided on the liquid pipe branch, and the throttling element is located between the first electronic expansion valve (1h) and the indoor heat exchanger (1d). "Based on the current mode of the air conditioning system, the current mode and target mode of the target indoor heat exchanger (1d), the operating modes of the high-pressure valve (1g), the low-pressure valve (1f), the first electronic expansion valve (1h), and the first four-way valve (7a) corresponding to the target indoor heat exchanger (1d)" includes: In the main cooling mode, when the indoor heat exchanger (1d) switches from heating mode or heating standby mode to cooling mode, the low-pressure valve (1f) opens to a preset opening degree, the high-pressure valve (1g) closes, the first electronic expansion valve (1h) opens to its maximum opening degree, then the throttling element closes, and after waiting for a third preset time period, the low-pressure valve (1f) is controlled to open and the high-pressure valve (1g) is closed.

13. The control method for an air conditioning system according to claim 12, characterized in that, A throttling element is provided on the liquid pipe branch, and the throttling element is located between the first electronic expansion valve (1h) and the indoor heat exchanger (1d). "Based on the current mode of the air conditioning system, the current mode and target mode of the target indoor heat exchanger (1d), the operating modes of the high-pressure valve (1g), the low-pressure valve (1f), the first electronic expansion valve (1h), and the first four-way valve (7a) corresponding to the target indoor heat exchanger (1d)" includes: In the main heating mode, when the indoor heat exchanger (1d) switches from heating mode or heating standby mode to cooling mode, the low-pressure valve (1f) opens to a preset opening degree, the high-pressure valve (1g) closes, the first electronic expansion valve (1h) opens to its maximum opening degree, then the throttling element closes, and after waiting for a third preset time period, the low-pressure valve (1f) is controlled to open and the high-pressure valve (1g) is closed.

14. The control method for an air conditioning system according to any one of claims 1 to 13, wherein the high-pressure valve (1g) and the low-pressure valve (1f) are integrated into a three-way valve, wherein the first port of the three-way valve is connected to the indoor heat exchanger (1d), the second port is connected to the high-pressure branch, and the third port is connected to the low-pressure branch.

15. An air conditioning system comprising a control module, characterized in that, The control module is configured to perform the control method of the air conditioning system as described in any one of claims 1-14.

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