Variable refrigerant flow air conditioning system

Abstract

The present application discloses a variable refrigerant flow air conditioning system, comprising: an outdoor unit, comprising a compressor and an outdoor expansion element; a plurality of indoor units connected to the outdoor unit by means of refrigerant piping, and each indoor unit comprising an indoor expansion element; and a control apparatus configured for controlling the outdoor unit and the plurality of indoor units. When heating, after receiving a shutdown or stop command, the control apparatus executes an evacuation operation, so that refrigerant on the outdoor unit side moves toward the indoor unit side. The control apparatus may be configured to perform control so as to achieve an equilibrium state between pressure at a suction side and pressure at a discharge side of the compressor.

Description

Multi-split air conditioning system

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese patent application filed on October 30, 2024, with application number 202411535170X and entitled "Multi-split Air Conditioning System", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of refrigeration equipment technology, and in particular to a multi-split air conditioning system. Background Technology

[0004] When a multi-split air conditioning system starts up, a significant pressure difference between the compressor's suction and discharge sides can lead to start-up failure, affecting the system's normal operation and reducing reliability. In multi-split air conditioning systems, when the compressor's starting pressure difference exceeds a certain range, the compressor's starting torque becomes less than the sum of the starting pressure difference torque and the frictional resistance torque, resulting in a stall phenomenon and abnormally high starting current and power. In this situation, on the one hand, the motor coils will overheat, affecting the insulation performance of the compressor's enameled wires and potentially burning out the coils; on the other hand, excessive power and current will increase the load on the power supply and wiring. If this exceeds the capacity of the power supply and wiring, it can also lead to undesirable accidents.

[0005] To avoid the aforementioned problems, relevant technologies incorporate a pressure balancing device between the intake and exhaust pipes of a multi-split air conditioning system. This pressure balancing device is a bypass branch consisting of a capillary tube, a solenoid valve, and a filter. Upon receiving a shutdown or stop signal, the solenoid valve on the bypass branch opens, ensuring that the high and low pressures of the multi-split air conditioning system are quickly balanced after the compressor stops operating.

[0006] However, when equalizing the pressure through the bypass branch, the sound generated by the refrigerant flow suddenly becomes sharp, resulting in a poor user experience and even triggering complaints.

[0007] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application, and therefore may include related technologies that are not known to those skilled in the art. Summary of the Invention

[0008] According to various embodiments of this application, a multi-split air conditioning system is designed and provided, which can significantly suppress noise and bring a good user experience.

[0009] According to various embodiments of this application, a multi-split air conditioning system is provided, comprising: an outdoor unit including a compressor and an outdoor throttling element; a plurality of indoor units connected to the outdoor unit via refrigerant piping, each of the plurality of indoor units including an indoor throttling element; a control device configured to control the outdoor unit and the plurality of indoor units; and, during heating, upon receiving a shutdown command or a stop command, the control device performs a vacuum operation to move the refrigerant from the outdoor unit side to one or more of the plurality of indoor units.

[0010] In some embodiments of this application, the control device may also be configured to perform the following controls to balance the pressure on the suction side and the pressure on the discharge side of the compressor: during vacuum operation, controlling the indoor throttling element of one or more indoor units to be in the open valve state, and controlling the outdoor throttling element to be in the set opening degree; after the vacuum operation is completed, keeping the indoor throttling element in the open valve state, keeping the outdoor throttling element in the set opening degree, and then controlling the outdoor throttling element to operate in the closed valve state.

[0011] In the multi-split air conditioning system provided in this application, upon receiving a shutdown or stop command, a vacuum operation can be performed via a control device. During and after the vacuum operation, the indoor throttling element remains open, while the outdoor throttling element remains at a set opening. This effectively balances the pressure on the compressor's suction and discharge sides, preventing sudden changes in refrigerant flow and reducing pressure fluctuations. Therefore, stable refrigerant flow and pressure balance reduce vibration and noise sources in the multi-split air conditioning system, ensuring smooth operation during shutdown or stoppage, significantly suppressing noise, and improving overall performance and user experience.

[0012] In one or more embodiments of this application, the control device may also be configured to configure a set opening degree based on the number of indoor units in the plurality of indoor units that are in operation. The set opening degree corresponds to the number of indoor units in operation; the more indoor units in operation, the larger the set opening degree. In other words, the size of the set opening degree may be positively correlated with the number of indoor units in operation.

[0013] The multi-split air conditioning system according to this application configures the opening degree according to the number of indoor units in operation. It can assess the refrigerant impact on the indoor unit based on the pressure difference shared by each indoor unit in operation, thereby reducing the noise generated by refrigerant impact and refrigerant flow under different operating conditions, thus significantly improving the stability of the system and the user experience.

[0014] In one or more embodiments of this application, the control device may be configured to: acquire the number of indoor units in operation; compare the number of indoor units in operation with a preset number; when the number of indoor units in operation is higher than the preset number, set a first preset opening degree based on the number of indoor units in operation; control the outdoor throttling element to first operate at the first preset opening degree, and then operate in a closed valve state; when the number of indoor units in operation is not higher than the preset number, set a second preset opening degree based on the number of indoor units in operation; control the outdoor throttling element to first operate at the second preset opening degree, and then operate in a closed valve state. The first preset opening degree may be greater than the second preset opening degree.

[0015] The multi-split air conditioning system according to this application can automatically select and generate the corresponding set opening degree by comparing the number of indoor units in operation with the set number, thereby ensuring smooth refrigerant flow and improving the stability and user experience of the multi-split air conditioning system.

[0016] In one or more embodiments of this application, during heating, the control device may perform a vacuum operation upon receiving a shutdown command, causing the refrigerant on the outdoor unit side to move to one or more indoor units. The control device may also be configured to, during the vacuum operation, control the indoor throttling elements of one or more indoor units to be in an open valve state, and control the outdoor throttling element to be at a shutdown set opening degree. After the vacuum operation ends, the indoor throttling elements are kept in an open valve state, the outdoor throttling element is kept at the shutdown set opening degree, and then the outdoor throttling element is controlled to operate in a closed valve state. The shutdown set opening degree is less than the stop set opening degree.

[0017] Alternatively, during heating, the control device can perform a vacuum operation upon receiving a shutdown command, causing the refrigerant on the outdoor unit side to move to one or more indoor units. The control device can also be configured to, during the vacuum operation, control the indoor throttling elements of one or more indoor units to be in the open valve state, and control the outdoor throttling element to be at the shutdown set opening degree; after the vacuum operation ends, maintain the indoor throttling elements in the open valve state, maintain the outdoor throttling element at the shutdown set opening degree, and then control the outdoor throttling element to operate in the closed valve state. The shutdown set opening degree is less than the shutdown set opening degree.

[0018] Upon receiving a shutdown command, the multi-split air conditioning system according to this application enters a standby state. At this time, other devices in the system are not completely shut down; for example, some devices may operate at low power. The operation of these devices helps maintain the pressure difference between the compressor's suction and discharge sides at a relatively low level. In this case, a relatively large shutdown setting can be allowed, thereby enabling the compressor's suction and discharge pressures to reach equilibrium more quickly, within permissible noise levels. Furthermore, since some devices are operating at low power, they themselves generate low-level noise, preventing the noise generated by refrigerant flow from suddenly becoming sharp and remaining at an acceptable level for the user.

[0019] In one or more embodiments of this application, the outdoor unit may further include an outdoor fan. During heating, the control device may perform a vacuum operation after receiving a shutdown command, causing the refrigerant on the outdoor unit side to move to one or more indoor units; the control device may also be configured to control the outdoor fan to stop operating during and after the vacuum operation.

[0020] According to this application, by having the control device perform the above steps, upon receiving a shutdown command (SW OFF), the control device can effectively achieve the following control objectives: while rapidly balancing the pressure on the compressor's suction side and the pressure on the discharge side, and controlling the noise at a low level, it can promptly stop the operation of the outdoor fan, thereby preventing users from mistakenly believing that the indoor unit is still working and creating the illusion that it has not been shut down.

[0021] In one or more embodiments of this application, each of one or more indoor units may further include an indoor fan. During heating, the control device may perform a vacuum operation upon receiving a shutdown command, causing the refrigerant on the outdoor unit side to move to one or more indoor unit sides; the control device may also be configured to control the indoor fan to stop operating during and after the vacuum operation.

[0022] According to this application, by having the control device perform the above steps, upon receiving a shutdown command (SW OFF), the control device can effectively achieve the following control objectives: while rapidly balancing the pressure on the compressor's suction side and the pressure on the discharge side, controlling the noise at a low level, and promptly stopping the operation of the indoor fan, preventing low-temperature air from being sent into the air-conditioned room, and also preventing users from mistakenly believing that the indoor unit is still working and creating the illusion that it has not been shut down.

[0023] In one or more embodiments of this application, the outdoor unit may further include an outdoor fan. During heating, the control device may, upon receiving a shutdown command, perform a vacuum operation to move the refrigerant on the outdoor unit side to one or more indoor units; the control device may also be configured to control the outdoor fan to stop operating during and after the vacuum operation.

[0024] According to this application, upon receiving a shutdown command (Thermo OFF), by having the control device execute the above steps, the control device can efficiently achieve the following objectives: quickly balance the pressure on the suction side and the pressure on the discharge side of the compressor, while maintaining a low noise level, and promptly stop the operation of the outdoor fan, thereby preventing users from misunderstanding that the multi-split air conditioning system is still working and avoiding the illusion that it has not been shut down.

[0025] In one or more embodiments of this application, each of one or more indoor units may further include an indoor fan. During heating, the control device may, upon receiving a shutdown command, perform a vacuum operation to move the refrigerant from the outdoor unit side to one or more indoor units; the control device may also be configured to control the indoor fan to operate at a set speed during and after the vacuum operation.

[0026] According to this application, an indoor fan operating at a set speed can help reduce exhaust pressure and decrease the pressure difference between the intake and exhaust sides of the compressor, thereby achieving pressure balance more quickly with lower noise.

[0027] According to various embodiments of this application, a multi-split air conditioning system can also be provided, comprising: an outdoor unit including a compressor and an outdoor electronic expansion valve; a plurality of indoor units connected to the outdoor unit via refrigerant piping, each of the plurality of indoor units including an indoor electronic expansion valve; and a control device configured to control the outdoor unit and the plurality of indoor units. During heating, the control device can, upon receiving a shutdown command, perform a vacuum operation, causing refrigerant on the outdoor unit side to move to one or more of the plurality of indoor units. The control device can also be configured to perform the following control to balance the pressure on the compressor's suction side and the pressure on its discharge side: during the vacuum operation, controlling the indoor electronic expansion valves of one or more indoor units to be in an open state, and the outdoor electronic expansion valve to be in a shutdown set opening degree; after the vacuum operation ends, maintaining the indoor electronic expansion valves in an open state, maintaining the outdoor electronic expansion valve in a shutdown set opening degree, and then gradually decreasing the opening degree of the outdoor electronic expansion valve over time until the outdoor electronic expansion valve reaches a closed state.

[0028] According to this application, by performing vacuum operation through a control device, and keeping the indoor electronic expansion valve in the open state and the outdoor electronic expansion valve at a set opening state during and after vacuum operation, the pressure on the suction side and the discharge side of the compressor can be effectively balanced. Furthermore, the opening of the outdoor electronic expansion valve can be gradually reduced over time, making the stepper motor deceleration process smoother and avoiding the problem of difficulty in accurately positioning the stepper motor's deceleration process. This further effectively avoids sudden changes in refrigerant flow and reduces pressure fluctuations. Stable refrigerant flow and pressure balance can reduce vibration and noise sources in multi-split air conditioning systems, ensuring stable operation of the multi-split air conditioning system during shutdown or stoppage, significantly suppressing noise, and improving overall performance and user experience.

[0029] According to various embodiments of this application, a multi-split air conditioning system can also be provided, comprising: an outdoor unit including a compressor and an outdoor electronic expansion valve; a plurality of indoor units connected to the outdoor unit via refrigerant piping, each of the plurality of indoor units including an indoor electronic expansion valve; and a control device configured to control the outdoor unit and the plurality of indoor units; during heating, the control device can, upon receiving a shutdown command, perform a vacuum operation to move the refrigerant from the outdoor unit side to one or more of the plurality of indoor units. The control device can also be configured to perform the following control to balance the pressure on the compressor's suction side and the pressure on the discharge side: during the vacuum operation, controlling the indoor electronic expansion valves of one or more indoor units to be in an open state, and controlling the outdoor electronic expansion valve to be at a shutdown set opening degree; after the vacuum operation ends, maintaining the indoor electronic expansion valves in an open state, maintaining the outdoor electronic expansion valve at the shutdown set opening degree, and then gradually decreasing the opening degree of the outdoor electronic expansion valve over time until the outdoor electronic expansion valve reaches a closed state.

[0030] The above technical solution has the following advantages or beneficial effects: By controlling the indoor electronic expansion valve to remain open after receiving a shutdown command, and gradually reducing the opening of the outdoor electronic expansion valve, the pressure on the compressor's suction side and discharge side reaches a balanced state. This stepwise control method effectively prevents damage to the compressor caused by pressure imbalance during shutdown, improves the system's reliability and stability, effectively suppresses noise, and enhances the user experience.

[0031] Other features and advantages of this application will become clearer after reading the detailed embodiments in conjunction with the accompanying drawings. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 is a structural schematic diagram of a multi-split air conditioning system provided in one or more embodiments of this application;

[0034] Figure 2 is a schematic diagram of the refrigerant circulation during heating in a multi-split air conditioning system provided in one or more embodiments of this application;

[0035] Figure 3 is a structural schematic diagram of a multi-split air conditioning system provided in one or more embodiments of this application;

[0036] Figure 4 shows an example of the test curve for the noise test;

[0037] Figure 5 shows an example of the test curve for the noise test;

[0038] Figure 6 is a timing control diagram of the indoor throttling element in a multi-split air conditioning system provided in one or more embodiments of this application;

[0039] Figure 7 is a timing control diagram of the outdoor throttling element in a multi-split air conditioning system provided in one or more embodiments of this application;

[0040] Figure 8 is a timing control diagram of the outdoor throttling element in a multi-split air conditioning system provided in one or more embodiments of this application;

[0041] Figure 9 is a timing control diagram of the indoor throttling element in a multi-split air conditioning system provided in one or more embodiments of this application;

[0042] Figure 10 is a timing control diagram of the outdoor throttling element in a multi-split air conditioning system provided in one or more embodiments of this application;

[0043] Figure 11 is a timing control diagram of the outdoor throttling element in a multi-split air conditioning system provided in one or more embodiments of this application.

[0044] Figure 12 is a timing control diagram of the indoor electronic expansion valve in a multi-split air conditioning system provided in one or more embodiments of this application;

[0045] Figure 13 is a timing control diagram of the outdoor electronic expansion valve in a multi-split air conditioning system provided in one or more embodiments of this application;

[0046] Figure 14 is a timing control diagram of the indoor electronic expansion valve in a multi-split air conditioning system provided in one or more embodiments of this application;

[0047] Figure 15 is a timing control diagram of the outdoor electronic expansion valve in a multi-split air conditioning system provided in one or more embodiments of this application. Detailed Implementation

[0048] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0049] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0050] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0051] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" 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 mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0052] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0053] The following disclosure provides many different implementations or examples for different structures of this application. To simplify the disclosure, components and arrangements in specific embodiments are described below. These are merely examples and are not intended to limit the scope of this application. Furthermore, the same or similar reference numerals and / or reference letters may be repeated in different embodiments or examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0054] A multi-split air conditioning system is a system that performs a refrigeration cycle using a compressor (e.g., compressor 100 shown in Figure 1), a condenser, a throttling device, and an evaporator. In other words, a multi-split air conditioning system may include a compressor, a condenser, a throttling device, and an evaporator. The refrigeration cycle includes a series of processes, including compression, condensation, expansion, and evaporation, to cool or heat an indoor space.

[0055] From a principle perspective, low-temperature, low-pressure refrigerant enters the compressor, which compresses it into a high-temperature, high-pressure refrigerant gas and discharges the compressed refrigerant gas. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and heat is released to the surrounding environment through the condensation process.

[0056] The throttling device expands the high-temperature, high-pressure liquid refrigerant that condenses in the condenser into a low-pressure liquid refrigerant. The evaporator evaporates the expanded refrigerant in the throttling device and returns the low-temperature, low-pressure refrigerant gas to the compressor. The evaporator achieves its cooling effect by utilizing the latent heat of refrigerant evaporation to exchange heat with the material being cooled. Throughout the cycle, the multi-split air conditioning system regulates the temperature of the indoor space.

[0057] A multi-split air conditioning system may include an outdoor unit, which refers to the portion of the refrigeration cycle that includes a compressor and an outdoor heat exchanger (e.g., outdoor heat exchanger 101 shown in Figure 1). The multi-split air conditioning system may also include indoor units. Indoor units may be located within an air-conditioned room and include an indoor heat exchanger (e.g., indoor heat exchanger 201 shown in Figure 1). Throttling devices may be provided in both the indoor and outdoor units and may include outdoor throttling elements and indoor throttling elements. For example, in this embodiment, both the outdoor throttling element (e.g., outdoor throttling element 102 shown in Figure 1) and the indoor throttling element (e.g., indoor throttling element 202 shown in Figure 1) are implemented by electronic expansion valves. More specifically, each indoor unit may include an expansion valve, referred to as an indoor electronic expansion valve, while the outdoor unit may include an outdoor electronic expansion valve. The term "air-conditioned room" as used herein refers to a room in which indoor units are installed.

[0058] Outdoor and indoor throttling elements can also be implemented by other valve elements or combinations of valve elements that can achieve the same function.

[0059] In one or more embodiments of this application, the electronic expansion valve can be driven by a stepper motor (or other motor capable of performing the same function) disposed within it. For example, upon receiving a control signal, the stepper motor rotates according to a specified number of steps, driving the valve core of the electronic expansion valve to move, thereby changing the opening degree of the electronic expansion valve. Each step of the stepper motor corresponds to a small change in the valve opening degree, thus the desired opening degree adjustment can be achieved by accumulating the number of steps of the stepper motor.

[0060] The indoor and outdoor heat exchangers can be used as condensers or evaporators. When the indoor heat exchanger is used as a condenser, the multi-split air conditioning system acts as a heater in heating mode (i.e., during heating). When the indoor heat exchanger is used as an evaporator, the multi-split air conditioning system acts as a cooler in cooling mode (i.e., during cooling).

[0061] In one alternative implementation, each outdoor unit may be equipped with one or more compressors, and AC power is supplied to the compressors in operation via a frequency converter. When the output frequency of the frequency converter changes, the compressor speed can change, thereby achieving different air conditioning capacities.

[0062] The outdoor unit may also include an outdoor fan (e.g., outdoor fan 103 shown in Figure 1) and a four-way valve (e.g., four-way valve 104 shown in Figure 1). In addition, the outdoor unit may also include other conventional components such as a gas-liquid separator (e.g., gas-liquid separator 105 shown in Figure 1), a capillary tube (not shown), and an oil separator (not shown).

[0063] A gas-liquid separator is a shell-shaped component configured to separate the refrigerant into gas and liquid components, and is typically located on the suction side of the compressor.

[0064] An outdoor heat exchanger can be configured to exchange heat between the refrigerant flowing through its internal heat exchange pipes and the air (or other medium) guided by an outdoor fan. The outdoor fan can be an axial fan, a cross-flow fan, or other optional fan type, and is usually located near the outdoor heat exchanger.

[0065] A four-way valve is a valve that switches the refrigerant flow direction according to the operating mode of a multi-split air conditioning system. In cooling mode, the compressor discharge side can be connected to one end of the outdoor heat exchanger via a four-way valve and other piping, while the compressor suction side can be connected to one end of the indoor heat exchanger via the same piping. Thus, the outdoor heat exchanger functions as a condenser, and the indoor heat exchanger functions as an evaporator. Similarly, in heating mode, the compressor discharge side can be connected to one end of the indoor heat exchanger via a four-way valve and piping, while the compressor suction side can be connected to one end of the outdoor heat exchanger via the same piping. Thus, the indoor heat exchanger functions as a condenser, and the outdoor heat exchanger functions as an evaporator.

[0066] The refrigerant circuit of a multi-split air conditioning system is connected sequentially to the compressor, outdoor heat exchanger, expansion valve, and indoor heat exchanger to allow the refrigerant to circulate.

[0067] The indoor electronic expansion valve and the outdoor electronic expansion valve installed in the indoor unit are both valves that reduce the pressure of the refrigerant flowing into the valve body itself. They are installed on the piping through which liquid refrigerant or gas-liquid two-phase refrigerant flows.

[0068] An oil separator can be configured to separate lubricating oil from the refrigerant discharged from the compressor, and is typically located on the compressor's discharge side. The lubricating oil separated by the oil separator can be guided through piping to a gas-liquid separator. A one-way valve can also be installed to guide the separated refrigerant to a four-way valve.

[0069] The outdoor unit may include an outdoor control circuit. The outdoor control circuit is typically housed in a well-sealed electrical box.

[0070] The outdoor control circuit may include components such as a processor, storage unit, input / output interfaces, and communication interfaces. The processor may be a dedicated processor, a central processing unit (CPU), etc. The processor can access the storage unit to execute instructions or applications stored therein to achieve related functions. The storage unit may include volatile memory and / or non-volatile memory. The input / output interfaces can communicate with various sensors installed in the outdoor unit to receive their detection values. The input / output interfaces can also communicate with devices such as frequency converters, compressors, outdoor fans, four-way valves, and outdoor electronic expansion valves to output control commands generated by the processor. The communication interfaces can support different wireless communication protocols, such as WiFi, Bluetooth, near-field communication, NB-IoT, etc., to communicate with other electronic devices, including but not limited to cloud servers, computers (e.g., host computers), smartphones, tablets, PDAs, intelligent control fixtures, wearable devices, and vehicle-mounted devices.

[0071] In one alternative implementation, the multi-split air conditioning system may include an outdoor unit.

[0072] In one alternative implementation, the multi-split air conditioning system may include multiple outdoor units, each of which may operate independently or be configured to operate in groups, such as two outdoor units as a group, four outdoor units as a group, and so on.

[0073] In one alternative implementation, each outdoor unit or group of outdoor units may be equipped with a corresponding indoor unit. Multiple indoor units may be connected to the outdoor unit via refrigerant piping.

[0074] In this application, the term "refrigerant" refers to the working fluid used in an air conditioning system to transfer heat and produce a cooling effect. Refrigerant may flow in refrigerant piping.

[0075] In one alternative implementation, the indoor unit can employ an independent air supply structure, such as a wall-mounted air supply structure, a floor-standing air supply structure, a ducted air supply structure, or an air supply structure embedded in the ceiling. The air supply structure may include a housing, which may have a return air inlet for drawing in air and an air supply outlet for delivering heat-exchanged air into the air-conditioned room. An indoor fan (e.g., indoor fan 203 shown in Figure 1) and an indoor heat exchanger are disposed within the housing. The indoor fan is located near the indoor heat exchanger.

[0076] In one alternative embodiment, the indoor unit may further include a wired controller, which can be fixedly installed on the wall of the air-conditioned room. The wired controller may be equipped with an operating interface for inputting the set temperature and operating mode, as well as a display interface for displaying the real-time temperature of the air-conditioned room and the operating status of the multi-split air conditioning system.

[0077] In one optional implementation, the indoor unit may further include a remote control, which can communicate with the indoor unit. The remote control may be equipped with buttons for inputting set temperature and operating mode, as well as a display interface for displaying the real-time temperature of the air-conditioned room and the operating status of the multi-split air conditioning system.

[0078] In one optional embodiment, the indoor unit may further include a mobile control terminal, which can communicate with the indoor unit and has an application interface. The mobile control terminal can input the set temperature and operating mode through the application interface and display the real-time temperature or operating status of the air-conditioned room.

[0079] In one alternative implementation, the mobile control terminal may be a computer, tablet computer, smartphone, wearable device, etc.

[0080] The indoor unit may also include an indoor unit control circuit, an indoor fan, and a display panel. The indoor unit control circuit may be equipped with an indoor controller. The indoor controller may be configured to drive the indoor fan, display various parameters on the display panel, provide human-machine interaction, receive and process sampling signals from various sensors, and perform necessary communication functions.

[0081] The indoor unit control circuit may also include electrical components such as storage units, processors, input / output interfaces, and communication interfaces.

[0082] The storage unit may include volatile memory and / or non-volatile memory. The storage unit may be configured to store instructions or data associated with at least one component of the indoor unit, such as an application program. For example, the application program could be used to adjust the temperature of an air-conditioned room by adjusting different speed settings of the indoor fan.

[0083] An indoor processor can be a dedicated processor, a central processing unit (CPU), or the like. The indoor processor can access memory to execute instructions stored in that memory to perform related functions.

[0084] The input / output interface can communicate with various sensors installed in the indoor unit to receive their detection values. The input / output interface can be a serial communication interface. It can also communicate with components such as indicator lights, buzzers, and stepper motors to output control commands. The stepper motor can be the driving component for the air guide plate.

[0085] The communication interface can be a software interface that supports different wireless communication protocols, such as WiFi and Bluetooth.

[0086] The indoor unit control circuit is usually equipped with a power supply circuit to provide 12V and 5V voltage.

[0087] The outdoor unit control circuit and the indoor unit control circuit can communicate with each other.

[0088] In some optional embodiments of this application, the outdoor unit control circuit and the indoor unit control circuit can work together as a control device to control the multi-split air conditioning system.

[0089] In some optional embodiments of this application, the control device may also be a server or a host computer. The server or host computer is communicatively connected to the outdoor unit control circuit and the indoor unit control circuit.

[0090] The multi-split air conditioning system provided in this application can effectively prevent the refrigerant flow sound from suddenly becoming sharp when the compressor's suction and exhaust pressures are balanced through a bypass branch. This provides users with a good user experience and avoids customer complaints.

[0091] Figure 1 is a structural schematic diagram of a multi-split air conditioning system provided in one or more embodiments of this application, and Figure 2 is a refrigerant circulation diagram of the multi-split air conditioning system provided in one or more embodiments of this application during heating, with the refrigerant flow direction shown as F in Figure 2. As shown in Figures 1 and 2, the multi-split air conditioning system includes multiple indoor units 20-1, 20-2, 20-3, and 20-4 and an outdoor unit 10. Each of the multiple indoor units 20-1, 20-2, 20-3, and 20-4 can be connected to the outdoor unit 10 through a refrigerant piping 40.

[0092] As shown in Figure 3, the multi-split air conditioning system may also include a control device 30, which is configured to control the outdoor unit 10 and multiple indoor units 20-1, 20-2, 20-3 and 20-4.

[0093] During heating, the control device 30 can perform pump down operation after receiving a shutdown command (SW OFF) or a stop command (Thermo OFF), causing the refrigerant on the outdoor unit side to move to the indoor unit side.

[0094] In one or more embodiments of this application, a power off command (SW OFF) refers to a command configured to turn off the power switch. The power off command can be implemented via a wired controller, a remote controller, or a power button on a mobile control terminal.

[0095] In one or more embodiments of this application, a shutdown command (Thermo OFF) refers to a command to stop heating when the air-conditioned room reaches the set temperature. The shutdown command can be an command automatically generated based on the detection value of a temperature sensor (or thermostat).

[0096] In one or more embodiments of this application, the outdoor unit 10 may include a compressor 100. Pump down operation refers to controlling the compressor 100 to continue running for a period of time after receiving a shutdown command (SW OFF) or a thermo OFF command, causing the refrigerant on the outdoor unit side to move towards the indoor unit side, and recovering the remaining refrigerant and refrigeration oil in the low-pressure piping towards the high-pressure side. In one or more embodiments of this application, pump down operation can be terminated based on pressure or temperature. For example, when the pressure or temperature reaches a preset value, the compressor 100 is turned off, completing the pump down operation and ensuring that most of the refrigerant has been drawn back. The control conditions for exiting pump down operation are not the focus of this application; control conditions for pump down operation in related technologies can be used, and will not be further described here. Pump down operation can ensure the safety and stability of the multi-split system when it is shut down or in standby mode, and can also prevent liquid return during startup or the occurrence of low oil viscosity in the compressor 100.

[0097] In one or more embodiments of this application, the multi-split air conditioning system may further include a throttling device. The throttling device may include an indoor throttling element 202 and an outdoor throttling element 102, as shown in FIG1. ​​Both the indoor throttling element 202 and the outdoor throttling element 102 may be implemented using electronic expansion valves. The control device 30 may also be configured to perform the following controls to balance the pressure on the suction side and the discharge side of the compressor 100:

[0098] During vacuum operation, the indoor throttling element 202 is in the open state, and the outdoor throttling element 102 is in the set opening degree; and

[0099] After the vacuuming operation is completed, keep the indoor throttling element 202 in the open valve state, keep the outdoor throttling element 102 in the set opening degree, and then control the outdoor throttling element 102 to work in the closed valve state.

[0100] It should be noted that in one or more embodiments of this application, the valve-closed state is not limited to the case where the electronic expansion valve is completely closed and the refrigerant flow is zero. The valve-closed state can also include the case where the electronic expansion valve operates at its minimum permissible opening. For some electronic expansion valves, the valve itself is designed with a minimum opening, allowing a very small flow even when operating in the valve-closed state to prevent refrigerant accumulation at the valve and avoid malfunctions such as liquid slugging and jamming. Furthermore, it should be noted that in this application, after the multi-split air conditioning system receives a shutdown command and performs the evacuation operation according to this application, the outdoor throttling element 102 can be in the open valve state, and the indoor throttling element 202 can be in a connected state with the outdoor throttling element 102. In this application, in heating mode, the indoor unit of the multi-split air conditioning system is under high pressure relative to the outdoor unit. In this case, when the multi-split air conditioning system receives a shutdown command or a stop command, it can perform evacuation operation, causing the refrigerant on the outdoor unit side to move towards the indoor unit side, which is under high pressure.

[0101] In one or more embodiments of this application, the valve opening state may include fully open and nearly fully open. Fully open refers to a state where the electronic expansion valve is set to its maximum opening, the valve is fully open, and the refrigerant flow experiences almost no resistance. Nearly fully open refers to a state where the electronic expansion valve is set to an opening close to its maximum opening, the valve is almost fully open, and the refrigerant flow experiences very little resistance.

[0102] In one or more embodiments of this application, the valve opening state may also include setting the opening degree to a predetermined large value, such as a boundary value of the usage range.

[0103] In one or more embodiments of this application, a balanced state refers to the pressure difference between the suction and discharge sides of the compressor 100 being within a reasonable range, ensuring the stable operation and high efficiency of the multi-split air conditioning system. That is, the pressure difference is within the range allowed by the design and operating specifications of the multi-split air conditioning system, avoiding excessively large or small pressure differences. In a balanced state, the compressor 100 can start and operate smoothly, avoiding overload or instability. For example, in a balanced state, the pressure difference between the suction and discharge sides of the compressor 100 can be within 0.3 MPa. This 0.3 MPa range is merely an example; the range of pressure difference may vary depending on the design and operating specifications of the multi-split air conditioning system.

[0104] In one or more embodiments of this application, the indoor throttling element 202 may include an indoor throttling element that is configured to be used with an indoor unit in an on state and in an off state (including a stopped state).

[0105] In the multi-split air conditioning system provided in this application, upon receiving a shutdown or stop command, the control device 30 performs a vacuum operation. During and after the vacuum operation, the indoor throttling element 202 remains in the open valve state, and the outdoor throttling element 102 remains at the set opening degree. This effectively balances the pressure on the suction side and the discharge side of the compressor 100, preventing sudden changes in refrigerant flow and reducing pressure fluctuations. Stable refrigerant flow and pressure balance reduce vibration and noise sources in the multi-split air conditioning system, ensuring smooth operation during shutdown or stop, significantly suppressing noise, and improving overall performance and user experience.

[0106] Figure 4 shows a comparison of measured noise levels. Without the control method described above according to this application, after one indoor unit receives a shutdown command, a stop command, or all indoor units receive a shutdown command, the refrigerant unloading sound suddenly becomes sharp within 3-4 seconds, then gradually decreases within 1 minute. This is particularly noticeable in wall-mounted indoor units, causing discomfort and a poor user experience. However, with the control method described above according to this application, the indoor units do not exhibit a sudden unloading impact sound, resulting in a very significant noise suppression effect.

[0107] In one or more embodiments of this application, the opening degree can be set within the range of 20%-30% of the total opening degree.

[0108] For example, assuming the total opening of the electronic expansion valve is 500 pls, the set opening can be in the range of 100 pls-150 pls.

[0109] Figure 5 shows a comparison of the measured noise levels. Compared to a valve opening of 39% (190 pls), the noise level decreased by 2.04 dB at a valve opening of 30% and by 5.1 dB at a valve opening of 20%.

[0110] Tables 1 to 3 show the test data of the suction side pressure Ps and the discharge side pressure Pd of the compressor 100 after the above control is implemented, where ΔP = Pd - Ps.

[0111] Table 1: First time a shutdown command was received

[0112] Table 2: Second time a shutdown command was received

[0113] Table 3: Third time a shutdown command was received

[0114] Tests showed that after 3 minutes of shutdown, the pressure difference between the suction and exhaust sides was within 0.3 MPa, and the pressure on the suction and exhaust sides of the compressor 100 reached a balanced state, meeting the drive requirements.

[0115] In one or more embodiments of this application, the control device 30 may be configured to set an opening degree based on the number of indoor units in the working state. The set opening degree may correspond to the number of indoor units in the working state; the more indoor units in the working state, the larger the set opening degree. In other words, the size of the set opening degree may be positively correlated with the number of indoor units in the working state.

[0116] In multi-split air conditioning systems, the number of indoor units connected can significantly affect refrigerant flow and pressure distribution. Under the condition that the pressure difference between the compressor's suction and discharge sides is the same, if more indoor units are connected, the pressure difference between the compressor's suction and discharge sides will be distributed across each indoor unit. This means that each indoor unit bears a smaller pressure difference. Because the pressure difference is distributed, each indoor unit experiences relatively less refrigerant impact when adjusting the opening of the outdoor throttling element, resulting in smoother refrigerant flow. Therefore, even if the setting is higher, the noise generated by the refrigerant flow is within a tolerable range, and a higher setting will allow the pressure to quickly equalize.

[0117] Conversely, the fewer indoor units connected, the more concentrated the pressure difference between the compressor's suction and discharge sides will be on fewer indoor units. This means each indoor unit experiences a larger pressure difference. Due to this concentrated pressure difference, the refrigerant impact force experienced by each indoor unit when opening the valve will also increase, leading to unstable refrigerant flow and potentially generating significant noise, thus affecting the user experience. To reduce refrigerant impact and noise, when fewer indoor units are connected, the valve opening can be set smaller to control the refrigerant flow, resulting in smoother refrigerant flow and reduced noise.

[0118] In this application, by configuring the opening degree according to the number of indoor units in operation, the refrigerant shock borne by the indoor unit can be evaluated based on the pressure difference shared by each indoor unit in operation. This reduces the noise generated by refrigerant shock and refrigerant flow under different operating conditions, thereby significantly improving the stability of the system and the user experience.

[0119] In Figures 6 to 15, EVI opening refers to the opening of the indoor throttling element (e.g., indoor electronic expansion valve), and EVO opening refers to the opening of the outdoor throttling element (e.g., outdoor electronic expansion valve). In other words, in this application, the indoor throttling element 202 can be an indoor electronic expansion valve, and the outdoor throttling element 102 can be an outdoor electronic expansion valve.

[0120] As shown in Figures 6 to 8, in one or more embodiments of this application, the control device 30 can be configured to perform the following control methods:

[0121] Obtain the number of indoor units that are in operation;

[0122] Compare the number of indoor units in operation with the set number;

[0123] When the number of indoor units in operation exceeds the set number, a larger first set opening degree is set based on the number of indoor units in operation (as shown by B1pls in Figure 8); the outdoor throttling element is controlled to first operate at the first set opening degree, and then operate in the closed valve state; and

[0124] When the number of indoor units in operation is less than the set number, a smaller second set opening degree is set according to the number of indoor units in operation (as shown in Figure 7, A1pls); the outdoor throttling element is controlled to first operate at the second set opening degree, and then operate in the closed valve state.

[0125] The first set opening degree can be greater than the second set opening degree.

[0126] As shown in Figures 7 and 8, if the number of indoor units in operation (or the number of connected indoor units, hereinafter referred to as the number of connected units) is not higher than the set number (for example, less than or equal to a units), the outdoor throttling element can be in the second set opening degree (as shown by A1pls in Figure 7) during the vacuuming operation. After the vacuuming operation is completed, the outdoor throttling element can be kept in the second set opening degree. After maintaining this for a T1 cycle (usually several minutes), the outdoor throttling element can be controlled to work in the closed valve state (as shown by Opls in Figure 7).

[0127] When the number of indoor units in operation is higher than the set number (e.g., greater than a units), the outdoor throttling element can be in the first set opening degree during the vacuuming operation (as shown by B1pls in Figure 8). After the vacuuming operation is completed, the outdoor throttling element can remain in the first set opening degree. After maintaining this for a T1 cycle (usually several minutes), the outdoor throttling element can be controlled to operate in the closed valve state (as shown by Opls in Figure 8).

[0128] According to this application, by comparing the number of indoor units in operation with the set number, the corresponding set opening degree can be automatically selected and generated to ensure smooth refrigerant flow and improve the stability and user experience of the multi-split air conditioning system.

[0129] In one or more embodiments of this application, the control device 30 may be configured to perform the following controls in response to different shutdown and stop commands.

[0130] As shown in Figures 9 to 11, during heating, the control device 30 can perform a no-load operation after receiving a shutdown command (SW OFF), causing the refrigerant on the outdoor unit side to move to the indoor unit side. The control device 30 can be configured to: control the indoor throttling element 202 to be in the open valve state and control the outdoor throttling element 102 to be in the shutdown set opening degree (A1pls as shown in Figure 10) during the evacuation operation; after the evacuation operation is completed, keep the indoor throttling element 202 in the open valve state, keep the outdoor throttling element 102 in the shutdown set opening degree, and then control the outdoor throttling element 102 to operate in the closed valve state.

[0131] As shown in Figures 9 to 11, similarly, during heating, the control device 30 can perform a vacuum operation after receiving a shutdown command (Thermo OFF), causing the refrigerant on the outdoor unit side to move to the indoor unit side. The control device can be configured to: control the indoor throttling element 202 to be in the open valve state and control the outdoor throttling element 102 to be in the shutdown set opening degree (A2pls as shown in Figure 10) during the vacuum operation; after the vacuum operation is completed, keep the indoor throttling element 202 in the open valve state, keep the outdoor throttling element 102 in the shutdown set opening degree, and then control the outdoor throttling element 102 to operate in the closed valve state.

[0132] The power-off setting opening A1pls can be less than the shutdown setting opening A2pls.

[0133] When the number of connected devices is greater, the corresponding shutdown setting opening B1pls can also be smaller than the stop setting opening B2pls, as shown in Figure 11.

[0134] In this application, upon receiving a shutdown command, the multi-split air conditioning system can be in standby mode. At this time, other devices in the multi-split air conditioning system are not completely shut down; for example, some devices may be operating at low power. The operation of these devices helps maintain the pressure difference between the compressor's suction and discharge sides at a relatively low level. In this case, a relatively large shutdown setting can be allowed, allowing the suction and discharge pressures of the compressor 100 to reach equilibrium more quickly within permissible noise levels. Simultaneously, because some devices are operating at low power, they themselves will also generate low-level noise, preventing the refrigerant flow noise from suddenly becoming sharp, but rather keeping it at a level acceptable to the user.

[0135] In one or more embodiments of this application, the outdoor unit may further include an outdoor fan 103. The control device 30 may be configured to, during heating, perform a vacuum operation upon receiving a shutdown command (SW OFF), causing the refrigerant on the outdoor unit 10 side to move towards the indoor unit side. The control device 30 may also be configured to control the outdoor fan 103 to stop operating during and after the vacuum operation.

[0136] By performing the steps described above in this application, when a shutdown command (SW OFF) is received, the control device 30 can effectively achieve the following control objectives: while rapidly balancing the pressure on the suction side and the pressure on the discharge side of the compressor 100 and controlling the noise at a low level, it can promptly stop the operation of the outdoor fan 103, thereby preventing users from mistakenly believing that the indoor unit is still working and creating the illusion that it has not been shut down.

[0137] In one or more embodiments of this application, each indoor unit may include an indoor heat exchanger 201 and an indoor fan 203. The control device 30 may be configured to perform a vacuum operation upon receiving a shutdown command (SW OFF) during heating, causing the refrigerant on the outdoor unit 10 side to move towards the indoor unit side. The control device 30 may also be configured to control the indoor fan 203 to stop operating during and after the vacuum operation.

[0138] By executing the above steps, when the shutdown command (SW OFF) is received, the control device can effectively achieve the following control objectives: while ensuring that the pressure on the suction side and the pressure on the exhaust side of the compressor 100 reach a balance quickly and the noise is controlled at a low level, the operation of the indoor fan 203 is stopped in time to prevent low-temperature air from being sent into the air-conditioned room and to prevent users from mistakenly believing that the indoor unit is still working and causing the illusion that it has not been shut down.

[0139] In one or more embodiments of this application, the control device may be configured to perform a vacuum operation after receiving a shutdown command (Thermo OFF) during heating, causing the refrigerant on the outdoor unit side 10 to move to the indoor unit side. The control device 30 may also be configured to control the outdoor fan 103 to stop operating during and after the vacuum operation.

[0140] In this application, upon receiving a shutdown command (Thermo OFF), by executing the above steps, the control device 30 can efficiently achieve the following objectives: quickly balance the pressure on the suction side and the pressure on the discharge side of the compressor 100, while maintaining a low noise level, and promptly stop the operation of the outdoor fan 103, thereby preventing users from misunderstanding that the multi-split air conditioning system is still working and avoiding the illusion that it has not been shut down.

[0141] In one or more embodiments of this application, the control device 30 may be configured to perform a vacuum operation after receiving a shutdown command (Thermo OFF) during heating, causing the refrigerant on the outdoor unit 10 side to move to the indoor unit side. The control device may also be configured to control the indoor fan 203 to operate at a set level, such as the lowest fan speed, during and after the vacuum operation.

[0142] According to this application, the indoor fan 203 operating at a set speed helps to reduce the exhaust pressure and decrease the pressure difference between the intake and exhaust sides of the compressor 100, thereby enabling the compressor 100 to achieve pressure balance between its intake and exhaust sides more quickly with lower noise.

[0143] In one or more embodiments of this application, upon receiving a shutdown command, the control device 30 may be configured to perform the following control to balance the pressure on the suction side and the pressure on the discharge side of the compressor 100: during vacuum operation, the indoor electronic expansion valve is controlled to be in the open state, and the outdoor electronic expansion valve is controlled to be in the shutdown set opening degree; after the vacuum operation ends, the indoor electronic expansion valve is kept in the open state, the outdoor electronic expansion valve is kept in the shutdown set opening degree, and then the opening degree of the outdoor electronic expansion valve is reduced stepwise over time until the outdoor electronic expansion valve reaches the closed state.

[0144] As shown in Figures 12 and 13, in the multi-split air conditioning system provided in this application, after receiving a shutdown command, the control device 30 can also be configured to perform the following control to balance the pressure on the suction side and the pressure on the exhaust side of the compressor 100.

[0145] During vacuum operation, the indoor electronic expansion valve can be controlled to be in the open state, and the outdoor electronic expansion valve can be controlled to be in the off-set opening degree (e.g., A1pls).

[0146] After the evacuation operation is completed, the indoor electronic expansion valve can remain in the open state, and the outdoor electronic expansion valve can remain at the set opening (e.g., A1pls). After reaching time T1, the opening of the outdoor electronic expansion valve can be reduced for the first time according to the preset adjustment amount, keeping the outdoor electronic expansion valve at the reduced opening. After reaching time T2, the opening of the outdoor electronic expansion valve can be reduced again according to the preset adjustment amount. The above steps are repeated until the outdoor electronic expansion valve reaches the closed state, for example, reaching 0pls at time T4.

[0147] By controlling the vacuum operation, and maintaining the indoor electronic expansion valve in the open state and the outdoor electronic expansion valve at the set opening degree during and after the vacuum operation, the pressure on the compressor's suction and discharge sides can be effectively balanced. The opening degree of the outdoor electronic expansion valve can be further reduced in a stepwise manner over time, making the stepper motor deceleration process smoother and avoiding the problem of inaccurate positioning of the stepper motor's deceleration process. This further effectively avoids sudden changes in refrigerant flow, reduces pressure fluctuations, and the stable refrigerant flow and pressure balance reduce vibration and noise sources in the multi-split air conditioning system, ensuring stable operation during shutdown or stoppage, significantly suppressing noise, and improving overall performance and user experience.

[0148] In one or more embodiments of this application, upon receiving a shutdown command, the control device 30 may be configured to perform the following control to balance the pressure on the suction side and the pressure on the discharge side of the compressor 100: during vacuum operation, the indoor electronic expansion valve is controlled to be in the open state, and the outdoor electronic expansion valve is controlled to be in the shutdown set opening degree; after the vacuum operation ends, the indoor electronic expansion valve is kept in the open state, the outdoor electronic expansion valve is kept in the shutdown set opening degree, and then the opening degree of the outdoor electronic expansion valve is reduced stepwise over time until the outdoor electronic expansion valve reaches the closed state.

[0149] As shown in Figures 14 and 15, in the multi-split air conditioning system provided in this application, after receiving a shutdown command, the control device 30 can be configured to perform the following control to balance the pressure on the suction side and the pressure on the exhaust side of the compressor 100.

[0150] During vacuum operation, the indoor electronic expansion valve can be controlled to be in the open state, and the outdoor electronic expansion valve can be controlled to be in the shutdown set opening degree (e.g., A2pls).

[0151] After the evacuation operation is completed, the indoor electronic expansion valve remains open, and the outdoor electronic expansion valve remains at the shutdown set opening (e.g., A2pls). At time T1, the opening of the outdoor electronic expansion valve can be reduced for the first time according to a preset adjustment amount, maintaining the outdoor electronic expansion valve at the reduced opening. At time T2, the opening of the outdoor electronic expansion valve can be reduced again according to the preset adjustment amount. This process is repeated until the outdoor electronic expansion valve reaches the closed state, for example, 0pls at time T4.

[0152] Upon receiving a shutdown command, the indoor electronic expansion valve can be controlled to remain open, while the opening of the outdoor electronic expansion valve can be gradually reduced, allowing the pressure on the suction side and the discharge side of the compressor 100 to reach a balanced state. This stepwise control method effectively prevents damage to the compressor 100 due to pressure imbalance during shutdown, improves the reliability and stability of the multi-split air conditioning system, and effectively suppresses noise, enhancing the user experience. The multi-split air conditioning system according to this application can operate smoothly during shutdown or turn-off, significantly suppressing noise.

[0153] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0154] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. Multi-split air conditioning system, including: The outdoor unit includes a compressor and an outdoor throttling element; Multiple indoor units connected to the outdoor unit via refrigerant piping, each of the multiple indoor units including an indoor throttling element; as well as A control device is configured to control the outdoor unit and the plurality of indoor units; during heating, after receiving a shutdown command or a stop command, the control device performs a vacuum operation, causing the refrigerant on the outdoor unit side to move to one or more of the plurality of indoor units. The control device is further configured to perform control to balance the pressure on the intake side and the pressure on the exhaust side of the compressor.

2. The multi-split air conditioning system according to claim 1, wherein, The control includes: During the vacuuming operation, the indoor throttling elements of one or more indoor units are controlled to be in the open valve state, and the outdoor throttling element is controlled to be at a set opening degree; and After the evacuation operation is completed, keep the indoor throttling element in the open valve state and keep the outdoor throttling element in the set opening degree, and then control the outdoor throttling element to work in the closed valve state.

3. The multi-split air conditioning system according to claim 1 or 2, wherein, The control device is further configured to configure the set opening degree according to the number of indoor units in operation among the plurality of indoor units; the size of the set opening degree is positively correlated with the number of indoor units in operation.

4. The multi-split air conditioning system according to claim 3, wherein, The control device is also configured to: Obtain the number of indoor units that are in operation; The number of indoor units in operation is compared with a set number; When the number of indoor units in operation is higher than the set number, a first set opening degree is set according to the number of indoor units in operation; the outdoor throttling element is controlled to first operate at the first set opening degree, and then operate in the closed valve state. When the number of indoor units in operation is not higher than the set number, a second preset opening degree is set according to the number of indoor units in operation; the outdoor throttling element is controlled to first operate at the second preset opening degree, and then operate in the closed valve state. Wherein, the first set opening degree is greater than the second set opening degree.

5. The multi-split air conditioning system according to claim 1, wherein: When heating, after receiving a shutdown command, the control device performs the vacuum operation, causing the refrigerant on the outdoor unit side to move to one or more indoor units. The control device is further configured to, during the vacuuming operation, control the indoor throttling element of one or more indoor units to be in the open valve state and control the outdoor throttling element to be in the shutdown set opening degree; after the vacuuming operation is completed, keep the indoor throttling element in the open valve state, keep the outdoor throttling element in the shutdown set opening degree, and then control the outdoor throttling element to operate in the closed valve state. or When heating, after receiving a shutdown command, the control device performs the vacuum operation, causing the refrigerant on the outdoor unit side to move to the one or more indoor units. The control device is also configured to, when performing the evacuation operation, control the indoor throttling element of one or more indoor units to be in an open valve state, and control the outdoor throttling element to be in a shutdown set opening degree. After the evacuation operation is completed, keep the indoor throttling element in the open valve state, keep the outdoor throttling element in the shutdown set opening degree, and then control the outdoor throttling element to work in the closed valve state. Wherein, the power-off setting opening degree is less than the power-off setting opening degree.

6. The multi-split air conditioning system according to claim 5, wherein: The outdoor unit also includes: an outdoor fan; During heating, after receiving a shutdown command, the control device performs the vacuum operation, causing the refrigerant on the outdoor unit side to move to the one or more indoor units side; the control device is also configured to control the outdoor fan to stop operating during and after performing the vacuum operation.

7. The multi-split air conditioning system according to claim 5 or 6, wherein: Each of the one or more indoor units further includes: an indoor fan; During heating, after receiving the shutdown command, the control device performs the vacuum operation, causing the refrigerant on the outdoor unit side to move to the one or more indoor units side; the control device is also configured to control the indoor fan to stop operating during and after performing the vacuum operation.

8. The multi-split air conditioning system according to claim 5, wherein: The outdoor unit also includes: an outdoor fan; During heating, after receiving the shutdown command, the control device performs the vacuum operation, causing the refrigerant on the outdoor unit side to move to the one or more indoor units side; the control device is also configured to control the outdoor fan to stop operating during and after performing the vacuum operation.

9. The multi-split air conditioning system according to claim 5 or 8, wherein: Each of the one or more indoor units further includes: an indoor fan; During heating, after receiving a shutdown command, the control device performs the vacuum operation, causing the refrigerant on the outdoor unit side to move to the one or more indoor units side; the control device is also configured to control the indoor fan to operate at a set speed during and after performing the vacuum operation.

10. Multi-split air conditioning system, including: The outdoor unit includes a compressor and an outdoor electronic expansion valve; Multiple indoor units connected to the outdoor unit via refrigerant piping, each of the multiple indoor units including an indoor electronic expansion valve; as well as A control device is configured to control the outdoor unit and the plurality of indoor units; during heating, after receiving a shutdown command, the control device performs a vacuum operation, causing the refrigerant on the outdoor unit side to move to one or more of the plurality of indoor units. The control device is further configured to perform the following control to balance the pressure on the suction side and the pressure on the discharge side of the compressor: During the vacuuming operation, the indoor electronic expansion valves of one or more indoor units are controlled to be in the open state, and the outdoor electronic expansion valve is controlled to be in the off-set opening degree. After the evacuation operation is completed, keep the indoor electronic expansion valve in the open state and keep the outdoor electronic expansion valve at the shutdown set opening degree. Then, gradually reduce the opening degree of the outdoor electronic expansion valve over time until the outdoor electronic expansion valve reaches the closed state.

11. Multi-split air conditioning system, including: The outdoor unit includes a compressor and an outdoor electronic expansion valve; Multiple indoor units connected to the outdoor unit via refrigerant piping, each of the multiple indoor units including an indoor electronic expansion valve; as well as A control device is configured to control the outdoor unit and the plurality of indoor units; during heating, after receiving a shutdown command, the control device performs a vacuum operation, causing the refrigerant on the outdoor unit side to move to one or more of the plurality of indoor units. The control device is further configured to perform the following control to balance the pressure on the suction side and the pressure on the discharge side of the compressor: During the vacuuming operation, the indoor electronic expansion valves of one or more indoor units are controlled to be in the open state, and the outdoor electronic expansion valve is controlled to be at the shutdown set opening degree. After the evacuation operation is completed, the indoor electronic expansion valve is kept in the open state, and the outdoor electronic expansion valve is kept at the shutdown set opening degree. Then, the opening degree of the outdoor electronic expansion valve is reduced stepwise over time until the outdoor electronic expansion valve reaches the closed state.

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