Air conditioner outdoor unit and air conditioning system

Abstract

According to the air conditioner outdoor unit and the air conditioner system, if the starting conditions are met, in a refrigeration mode, the exhaust superheat degree of a compressor of the operating outdoor unit reaches the upper limit value of a first set temperature, and the superheat degree of an outdoor heat exchanger of the operating outdoor unit reaches the lower limit value of a second set temperature; if yes, a bypass valve of the shut-down outdoor unit is started, so that the refrigerant in the shut-down outdoor unit flows into the operating outdoor unit, and the refrigerant in the operating outdoor unit is sufficient; and after the bypass valve of the shut-down outdoor unit is opened, if the exhaust superheat degree of the compressor of the operating outdoor unit reaches the lower limit value of the third set temperature or the superheat degree of the outdoor heat exchanger of the operating outdoor unit reaches the upper limit value of the fourth set temperature, the bypass valve of the shut-down outdoor unit is closed. When the opening condition is met, the bypass valve of the shut-down outdoor unit is opened, the refrigerant in the shut-down outdoor unit flows into the operating outdoor unit, refrigerant distribution unbalance is avoided, and the technical problem that in the prior art, the refrigerant in the operating outdoor unit is insufficient is solved.

Description

Technical Field

[0001] This invention relates to the field of air conditioning technology, and more particularly to outdoor air conditioning units and air conditioning systems. Background Technology

[0002] A multi-module combined air conditioning system consists of multiple outdoor units connected in parallel and multiple indoor units connected in parallel. In actual operation, multiple outdoor unit modules are connected together to drive multiple indoor units.

[0003] If only a few indoor units (such as 1-2 units) are turned on and run in cooling mode for a long time, it will cause a serious refrigerant distribution imbalance and further lead to poor cooling performance.

[0004] To ensure reliability, all outdoor units in a multi-module air conditioning system need to be started. While running, these outdoor units continuously supply refrigerant to the system. However, once the system transitions to normal operation with low load on the indoor units, only one outdoor unit remains operational. This causes refrigerant to continuously flow into the shut-down outdoor unit, gradually reducing the amount of refrigerant in its circulation system. Furthermore, the shut-down outdoor unit experiences a refrigerant retention effect due to its lower heat exchanger temperature. This asymmetrical distribution worsens over time, directly manifesting as reduced cooling performance in the indoor units and abnormally widened electronic expansion valves producing high-frequency hissing noise. In more severe cases, insufficient refrigerant return to the compressor in the running outdoor unit can lead to excessive discharge temperature, causing the inverter drive module temperature to rise continuously, ultimately triggering a protective shutdown of the system and significantly reducing equipment reliability. Summary of the Invention

[0005] This invention proposes an outdoor air conditioning unit and air conditioning system, which solves the technical problem of insufficient refrigerant in the outdoor unit in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides an outdoor unit for air conditioning, comprising: Multiple outdoor units connected in parallel; a bypass pipeline is provided between the exhaust port and the intake port of the compressor of the outdoor unit; a bypass valve is provided on the bypass pipeline; The control module is configured as follows: Determine if the start-up conditions are met: In cooling mode, the superheat of the compressor discharge of the outdoor unit reaches the upper limit of the first set temperature, and the superheat of the outdoor heat exchanger of the outdoor unit reaches the lower limit of the second set temperature. If the opening conditions are met, the bypass valve of the outdoor unit that is shut down will be opened; After the bypass valve of the outdoor unit is opened, the bypass valve of the outdoor unit will be closed if any of the following closing conditions are met. Shutdown condition 1: The compressor exhaust superheat of the outdoor unit reaches the lower limit of the third set temperature; Shutdown condition two: The superheat of the outdoor heat exchanger of the outdoor unit reaches the upper limit of the fourth set temperature. The first set temperature is higher than the third set temperature; the second set temperature is lower than the fourth set temperature.

[0007] In some embodiments of this application, the closing condition further includes: Closure condition 3: The low-pressure of the outdoor unit is higher than the set pressure when the bypass valve is open.

[0008] In some embodiments of this application, the closing condition further includes: Closing condition four: The bypass valve of the outdoor unit is continuously open for the first set time.

[0009] In some embodiments of this application, the control module is further configured as follows: After the bypass valve of the outdoor unit is closed, a second set time is delayed before determining whether the opening conditions are met.

[0010] In some embodiments of this application, the opening condition further includes: a third set time period has elapsed since the last time the bypass valve of the outdoor unit was turned on and off.

[0011] In some embodiments of this application, the control module is further configured as follows: To determine if the outdoor unit being shut down meets the following condition: the high-pressure pressure reaches the upper limit of the average high-pressure pressure of the operating outdoor unit when it is shut down; If the conditions are met, the electronic expansion valve on the liquid pipe of the outdoor unit will remain open at the fourth set position for the fourth time before gradually closing.

[0012] In some embodiments of this application, the control module is further configured as follows: After the compressor has been running at a set low frequency for five set durations, it enters the oil return mode; in the oil return mode, the compressor is controlled to run at a set high frequency; wherein, the set high frequency is greater than the set low frequency; When the oil return time reaches the sixth preset time, exit the oil return mode.

[0013] In some embodiments of this application, the control module is further configured as follows: In the oil return mode, when the compressor's discharge temperature reaches the upper limit of the fifth set temperature, the compressor frequency is reduced.

[0014] Air conditioning system, including: Indoor unit, which includes multiple indoor units connected in parallel; The outdoor unit is an air conditioning outdoor unit as described above; the outdoor unit is connected to the indoor unit.

[0015] In some embodiments of this application, the outdoor unit includes two outdoor units connected in parallel.

[0016] The technical solution of the present invention has the following technical effects compared with the prior art: If the opening conditions of the air conditioning outdoor unit and air conditioning system of the present invention are met: in cooling mode, the superheat of the compressor discharge of the operating outdoor unit reaches the upper limit of the first set temperature, and the superheat of the outdoor heat exchanger of the operating outdoor unit reaches the lower limit of the second set temperature; then the bypass valve of the shut-off outdoor unit is opened, so that the refrigerant in the shut-off outdoor unit flows to the operating outdoor unit, so that the refrigerant in the operating outdoor unit is sufficient, thereby ensuring that the refrigerant circulating in the air conditioning system is sufficient; after the bypass valve of the shut-off outdoor unit is opened, if the superheat of the compressor discharge of the operating outdoor unit reaches the lower limit of the third set temperature or the superheat of the outdoor heat exchanger of the operating outdoor unit reaches the upper limit of the fourth set temperature, then the bypass valve of the shut-off outdoor unit is closed. Therefore, the air conditioning outdoor unit and air conditioning system of the present invention, when the start-up conditions are met, open the bypass valve of the stopped outdoor unit, so that the refrigerant in the stopped outdoor unit flows to the operating outdoor unit, avoids refrigerant distribution imbalance, ensures sufficient circulating refrigerant in the operating outdoor unit and the operating indoor unit, and solves the technical problem of insufficient refrigerant in the operating outdoor unit in the prior art.

[0017] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a system schematic diagram of one embodiment of the air conditioning system of the present invention; Figure 2 A flowchart illustrating one embodiment of the steps performed by the control module of the air conditioning outdoor unit of the present invention; Figure 3 A flowchart of yet another embodiment of the steps performed by the control module; Figure 4 A flowchart of yet another embodiment of the steps performed by the control module; Figure 5 A flowchart of yet another embodiment of the steps performed by the control module; Figure 6 A flowchart of yet another embodiment of the steps performed by the control module; Figure 7 A flowchart of yet another embodiment of the steps performed by the control module; Figure 8 A flowchart of yet another embodiment of the steps performed by the control module; Figure 9 A flowchart of yet another embodiment of the steps performed by the control module; Figure 10 A flowchart of yet another embodiment of the steps performed by the control module.

[0020] Figure label: 1. Compressor; 2. Four-way valve; 3. Outdoor heat exchanger; 4. Outdoor fan; 5. Electronic expansion valve; 6. Liquid-side shut-off valve; 7. Indoor electronic expansion valve; 8. Indoor heat exchanger; 10. Gas-side shut-off valve; 11. Gas-liquid separator. Detailed Implementation

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] In this invention, unless otherwise explicitly 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 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 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.

[0026] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0027] Air conditioners execute refrigeration and heating cycles using a compressor, condenser, expansion valve, and evaporator. These cycles are controlled by a controller, which manages the refrigerant flow and the opening of the expansion valve. The refrigeration and heating cycles involve a series of processes including compression, condensation, expansion, and evaporation, ultimately supplying refrigerant to the conditioned and heat-exchanged air.

[0028] The compressor compresses refrigerant gas under high temperature and pressure 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 the heat is released to the surrounding environment through the condensation process.

[0029] The expansion valve expands the high-temperature, high-pressure liquid refrigerant condensed in the condenser into a low-pressure liquid refrigerant. The evaporator evaporates the expanded refrigerant in the expansion valve, returning 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 air conditioner regulates the temperature of the indoor space.

[0030] An air conditioner outdoor unit refers to the part of the refrigeration cycle that includes the compressor and the outdoor heat exchanger. An air conditioner indoor unit includes the indoor heat exchanger, and an expansion valve can be provided in either the outdoor or indoor unit.

[0031] The indoor and outdoor heat exchangers function as either condensers or evaporators. When the indoor heat exchanger is used as a condenser, the air conditioner functions as a heater in heating mode; when the indoor heat exchanger is used as an evaporator, the air conditioner functions as a cooler in cooling mode.

[0032] The air conditioning system in this embodiment includes an indoor unit, an outdoor unit, etc., see [link / reference]. Figure 1 As shown.

[0033] The indoor unit comprises multiple indoor units connected in parallel. Each indoor unit includes an indoor heat exchanger 8, an indoor fan, and an indoor electronic expansion valve 7, etc.

[0034] The outdoor unit consists of multiple outdoor units connected in parallel, as well as a control module.

[0035] The outdoor unit includes a compressor 1, a four-way valve 2, an outdoor heat exchanger 3, an outdoor fan 4, an electronic expansion valve 5, a liquid-side shut-off valve 6, a gas-side shut-off valve 10, a gas-liquid separator 11, etc.

[0036] A bypass pipeline is provided between the exhaust port and the suction port of compressor 1; a bypass valve SVA is provided on the bypass pipeline.

[0037] The outdoor unit is connected to the indoor unit. The liquid pipe of the outdoor unit is connected to the liquid pipe of the indoor unit, and the gas pipe of the outdoor unit is connected to the gas pipe of the indoor unit.

[0038] In a standard refrigeration cycle, the high-temperature, high-pressure gaseous refrigerant discharged from compressor 1 first enters the outdoor heat exchanger 3 (condenser) through four-way valve 2, where it is condensed into a medium-temperature, high-pressure liquid state by air cooling. Subsequently, it is throttled and depressurized through electronic expansion valve 5, and then enters the indoor unit through liquid-side shut-off valve 6. Under the precise control of indoor electronic expansion valve 7, the refrigerant is depressurized into a low-temperature, low-pressure gas-liquid two-phase state, and enters indoor heat exchanger 8 to absorb ambient heat. The evaporated gaseous refrigerant flows out from indoor heat exchanger 8, enters four-way valve 2 through gas-side shut-off valve 10, enters gas-liquid separator 11 through four-way valve 2, and finally flows back to compressor 1 to complete the cycle.

[0039] In this application, the compressor is a fully enclosed scroll compressor, the outdoor heat exchanger is a finned outdoor heat exchanger, the outdoor fan is a DC inverter outdoor fan, and the indoor fan is a cross-flow indoor fan.

[0040] The control module is used to control the operation of the outdoor unit.

[0041] The control module is configured as follows: Determine if the start-up conditions are met: In cooling mode, the superheat of the compressor discharge of the outdoor unit reaches the upper limit of the first set temperature A, and the superheat of the outdoor heat exchanger of the outdoor unit reaches the lower limit of the second set temperature B. If the opening conditions are met, the bypass valve of the outdoor unit that is shut down will be opened; After the bypass valve of the outdoor unit is opened, the bypass valve of the outdoor unit will be closed if any of the following closing conditions are met. Shutdown condition 1: The superheat of the compressor exhaust of the outdoor unit reaches the lower limit of the third set temperature E; Shutdown condition two: The superheat of the outdoor heat exchanger of the outdoor unit reaches the upper limit of the fourth set temperature C. Among them, the first set temperature A is higher than the third set temperature E; the second set temperature B is lower than the fourth set temperature C.

[0042] Therefore, the control module specifically performs the following steps, see [link to relevant documentation]. Figure 2 As shown.

[0043] Step S11: Determine if the start-up conditions are met: In cooling mode, the superheat of the compressor exhaust of the outdoor unit reaches the upper limit of the first set temperature A, and the superheat of the outdoor heat exchanger of the outdoor unit reaches the lower limit of the second set temperature B.

[0044] The compressor discharge superheat reaches the upper limit of the first set temperature A, that is, the compressor discharge superheat is greater than or equal to the first set temperature A.

[0045] The outdoor heat exchanger superheat reaches the lower limit of the second set temperature B, that is, the outdoor heat exchanger superheat is ≤ the second set temperature B.

[0046] If the opening conditions are met, proceed to step S12: Open the bypass valve of the outdoor unit that is shut down.

[0047] Step S13: Determine whether any of the closing conditions are met.

[0048] If any of the following closing conditions are met, proceed to step S14: Close the bypass valve of the outdoor unit that is shut down.

[0049] Shutdown condition 1: The superheat of the compressor exhaust of the outdoor unit reaches the lower limit of the third set temperature E; that is, the superheat of the compressor exhaust is ≤ the third set temperature E.

[0050] Shutdown condition two: The superheat of the outdoor heat exchanger of the outdoor unit reaches the upper limit of the fourth set temperature C, that is, the superheat of the outdoor heat exchanger is greater than or equal to the fourth set temperature C.

[0051] In cooling mode, if the superheat of the compressor discharge of the operating outdoor unit is greater than or equal to the first set temperature A, and the superheat of the outdoor heat exchanger is less than or equal to the second set temperature B, it is determined that there is a risk of refrigerant shortage in the operating outdoor unit, and the opening conditions are met. The bypass valve of the shut-down outdoor unit needs to be opened so that the liquid refrigerant remaining in the heat exchanger of the shut-down outdoor unit can be depressurized and flashed through the high and low pressure bypass circuit and then enter the low pressure side of the operating outdoor unit to re-enter the circulation.

[0052] When the bypass valve SVA of the outdoor unit is opened, the refrigerant on the high-pressure side of the compressor flows to the low-pressure side of the compressor through the bypass pipeline under the action of pressure difference, and then flows to the gas-side shut-off valve 10 through the four-way valve 2. The gas pipe of the outdoor unit that is stopped is connected in parallel with the gas pipe of the outdoor unit that is started. The refrigerant in the gas pipe of the outdoor unit that is stopped flows to the gas pipe of the outdoor unit that is started, and then participates in the refrigerant circulation, so that the refrigerant on the high-pressure side of the compressor of the outdoor unit that is stopped flows into the system circulation.

[0053] When the superheat of the compressor discharge of the outdoor unit is less than or equal to the third set temperature E, or the superheat of the outdoor heat exchanger of the outdoor unit is greater than or equal to the fourth set temperature C, it indicates that the refrigerant in the outdoor unit is sufficient, and the bypass valve of the outdoor unit that is shut down can be closed.

[0054] By designing the first set temperature A to be higher than the third set temperature E, and the second set temperature B to be lower than the fourth set temperature C, the frequent start and stop of the bypass valve of the outdoor unit when it is shut down can be avoided.

[0055] In this embodiment, the outdoor unit and air conditioning system, if the following conditions are met: in cooling mode, the superheat of the compressor discharge of the operating outdoor unit reaches the upper limit of the first set temperature A, and the superheat of the outdoor heat exchanger of the operating outdoor unit reaches the lower limit of the second set temperature B; then the bypass valve of the off outdoor unit is opened, allowing refrigerant in the off outdoor unit to flow into the operating outdoor unit, ensuring sufficient refrigerant in the operating outdoor unit and thus guaranteeing sufficient refrigerant circulation in the air conditioning system. After the bypass valve of the off outdoor unit is opened, if the superheat of the compressor discharge of the operating outdoor unit reaches the lower limit of the third set temperature E or the superheat of the outdoor heat exchanger of the operating outdoor unit reaches the upper limit of the fourth set temperature C, then the bypass valve of the off outdoor unit is closed. Therefore, in this embodiment, the outdoor unit and air conditioning system, when the opening conditions are met, open the bypass valve of the off outdoor unit, allowing refrigerant in the off outdoor unit to flow into the operating outdoor unit, avoiding refrigerant distribution imbalance, ensuring sufficient circulating refrigerant in both the operating outdoor unit and the operating indoor unit, and solving the technical problem of insufficient refrigerant in the operating outdoor unit in the prior art.

[0056] In some embodiments of this application, the closing condition further includes: Closure condition 3: The low pressure of the outdoor unit is higher than the set pressure D when the bypass valve is open.

[0057] Therefore, the control module performs the following steps, see [link to relevant documentation]. Figure 3 As shown.

[0058] Step S13-1: After the bypass valve of the outdoor unit is opened, determine whether any of the following closing conditions are met: closing condition one, closing condition two, or closing condition three.

[0059] That is, determine whether any of the following closing conditions are met: Shutdown condition 1: The superheat of the compressor exhaust of the outdoor unit reaches the lower limit of the third set temperature E; Shutdown condition two: The superheat of the outdoor heat exchanger of the outdoor unit reaches the upper limit of the fourth set temperature C. Closing condition three: The low-pressure of the operating outdoor unit has increased by the set pressure D compared to when the bypass valve is open. That is, the current low-pressure of the operating outdoor unit has increased by the set pressure D compared to the low-pressure of the shut-down outdoor unit when the bypass valve is open.

[0060] If any of the closing conditions are met, proceed to step S14: close the bypass valve of the outdoor unit that is shut down.

[0061] When the current low pressure of the operating outdoor unit is higher than the low pressure when the bypass valve of the shut-off outdoor unit is opened, it indicates that there is sufficient refrigerant circulating in the air conditioning system. At this time, the bypass valve of the shut-off outdoor unit needs to be closed.

[0062] By designing the third shut-off condition, the system can accurately determine whether to shut down the bypass valve of the shut-down outdoor unit by utilizing the magnitude of the increase in low-pressure of the operating outdoor unit.

[0063] In some embodiments of this application, the closing condition further includes: Closing condition four: The bypass valve of the outdoor unit is continuously open for the first set time.

[0064] Therefore, the control module performs the following steps, see [link to relevant documentation]. Figure 4 As shown.

[0065] Step S13-2: After the bypass valve of the outdoor unit is opened, determine whether any of the following closing conditions are met: closing condition one, closing condition two, closing condition three, or closing condition four.

[0066] That is, determine whether any of the following closing conditions are met: Shutdown condition 1: The superheat of the compressor exhaust of the outdoor unit reaches the lower limit of the third set temperature E; Shutdown condition two: The superheat of the outdoor heat exchanger of the outdoor unit reaches the upper limit of the fourth set temperature C. Closing condition 3: The low pressure of the outdoor unit is higher than the set pressure when the bypass valve is open; Closing condition four: The bypass valve of the outdoor unit is continuously open for the first set time.

[0067] If any of the closing conditions are met, proceed to step S14: close the bypass valve of the outdoor unit that is shut down.

[0068] When the bypass valve of the shut-off outdoor unit remains open for the first set time (e.g., 3 to 6 minutes), it indicates that the bypass valve has been open long enough, and the excess refrigerant in the shut-off outdoor unit has flowed to the operating outdoor unit. The refrigerant circulating in the air conditioning system is sufficient. At this time, the bypass valve of the shut-off outdoor unit needs to be closed.

[0069] By designing the fourth closing condition, the system utilizes the opening duration of the bypass valve of the outdoor unit that is shut down to accurately determine whether to close the bypass valve of the outdoor unit that is shut down.

[0070] In some embodiments of this application, the control module is further configured as follows: After the bypass valve of the outdoor unit is closed, a second set time is delayed before determining whether the opening conditions are met.

[0071] That is, after step S14, step S15 is executed: delay for a second set duration, and then return to step S11, see below. Figure 5 As shown, this avoids frequent switching of the bypass valve on the outdoor unit during shutdown, which could cause system fluctuations.

[0072] Therefore, to avoid system fluctuations caused by frequent adjustment of the bypass valve, a second set time (e.g., 2 minutes) is set after the bypass valve SVA is closed, and then the process returns to step S11 to re-enter the detection process.

[0073] In some embodiments of this application, the activation condition further includes: a third set time period has elapsed since the last activation or shutdown of the outdoor unit's bypass valve.

[0074] Therefore, the activation conditions are: in cooling mode, the superheat of the compressor discharge of the outdoor unit reaches the upper limit of the first set temperature A, and the superheat of the outdoor heat exchanger of the outdoor unit reaches the lower limit of the second set temperature B, and the time elapsed since the last start-up and shutdown of the outdoor unit's bypass valve exceeds the third set time (e.g., 15 to 30 minutes).

[0075] When the opening conditions are met, namely: in cooling mode, the superheat of the compressor discharge of the outdoor unit reaches the upper limit of the first set temperature A, and the superheat of the outdoor heat exchanger of the outdoor unit reaches the lower limit of the second set temperature B, and the time elapsed since the last opening and closing of the bypass valve of the outdoor unit exceeds the third set time, the bypass valve of the closed outdoor unit will be opened.

[0076] By designing the bypass valve to have an opening condition that includes a three-set time interval between the last time the outdoor unit was turned on and off, frequent opening of the bypass valve can be avoided, thus preventing any impact on the stability of the air conditioning system.

[0077] In some embodiments of this application, the control module is further configured as follows: To determine if the outdoor unit is shut down, the following condition must be met: the high-pressure pressure at the time of shutdown must reach the upper limit of the average high-pressure pressure of the operating outdoor unit; that is, the high-pressure pressure at the time of shutdown must be greater than or equal to the average high-pressure pressure of the operating outdoor unit. If the conditions are met, the electronic expansion valve 5 on the liquid pipe of the outdoor unit will remain open at the fourth set opening for the fourth time before gradually closing.

[0078] Therefore, the control module specifically performs the following steps, see [link to relevant documentation]. Figure 6 As shown.

[0079] Step S21: Determine whether the outdoor unit being shut down meets the following condition: when shut down, the high pressure Pd (compressor exhaust pressure) is greater than or equal to the average high pressure Pdave of the operating outdoor unit.

[0080] If the conditions are met, proceed to step S22: the electronic expansion valve 5 on the liquid pipe of the outdoor unit to be shut down is kept at the fourth set opening for a duration (e.g., 15s to 60s) before being gradually closed.

[0081] By delaying the closure of the electronic expansion valve on the liquid line when the unit is shut down, the residual pressure of the system is used to push some of the liquid refrigerant accumulated in the heat exchanger of the outdoor unit back into the circulation system, thereby reducing the amount of refrigerant retained in the outdoor unit and effectively alleviating the problem of insufficient refrigerant in the circulation system.

[0082] In some embodiments of this application, the control module is further configured as follows: After the compressor has been running at a set low frequency for five set durations, it enters the oil return mode; in the oil return mode, the compressor is controlled to run at a set high frequency; wherein, the set high frequency is greater than the set low frequency; When the oil return time reaches the sixth preset time, exit the oil return mode.

[0083] Therefore, the control module specifically performs the following steps, see [link to relevant documentation]. Figure 7 As shown.

[0084] Step S31: Determine if the oil return condition is met: The compressor runs at a low frequency for the fifth set duration (e.g., 1 hour).

[0085] If the oil return condition is met, proceed to step S32: enter the oil return mode. In the oil return mode, control the compressor to operate at a set high frequency (e.g., 60Hz); the set high frequency is greater than the set low frequency.

[0086] Step S33: When the oil return time reaches the sixth set time (e.g., 2 minutes), exit the oil return mode.

[0087] By designing steps S31 to S33, when the compressor is running at a set low frequency for the fifth set duration, it enters the oil return mode and controls the compressor to run at a set high frequency to ensure oil return and avoid oil shortage in the compressor; when the oil return duration reaches the sixth set duration, it exits the oil return mode.

[0088] In some embodiments of this application, the control module is further configured as follows: In oil return mode, when the compressor's discharge temperature reaches the upper limit of the fifth set temperature, the compressor frequency is reduced.

[0089] That is, the control module performs the following steps, see [link / reference]. Figure 8 As shown.

[0090] Step S41: In oil return mode, determine whether the following condition is met: the exhaust temperature of the compressor of the outdoor unit reaches the upper limit of the fifth set temperature, that is, the exhaust temperature of the compressor is ≥ the fifth set temperature.

[0091] If the compressor's discharge temperature is ≥ the fifth set temperature, then proceed to step S42: reduce the compressor frequency.

[0092] By designing steps S41 to S42, in oil return mode, when the compressor's discharge temperature is greater than or equal to the fifth set temperature (e.g., 115°C), the compressor frequency is reduced to avoid shutdown protection when the discharge temperature is high, thereby reducing the number of times the outdoor unit starts and stops and cutting off the source of refrigerant retention.

[0093] When the indoor unit load is low, the compressor runs at a low frequency. In order to ensure the return of oil to the compressor, after the fifth set time (e.g., 1 hour) of low-frequency operation, the compressor automatically runs at a high frequency for the sixth set time (e.g., 2 minutes) to control the return of oil. In this case, if the number of indoor units is small, the amount of refrigerant circulating back to the compressor will be small, and the exhaust temperature will rise faster.

[0094] In existing technology, when the compressor's discharge temperature exceeds 105°C, the unit shuts down for oil return protection to ensure compressor reliability. This increases the number of compressor shutdowns, leading to frequent compressor start-stop cycles. In this application, the strategy of shutting down for protection at high discharge temperatures is eliminated. Instead, a control strategy is adopted to reduce the compressor frequency when the compressor discharge temperature is greater than or equal to the fifth set temperature (e.g., 115°C). This reduces the number of compressor start-stop cycles, avoids frequent compressor start-stop cycles, and cuts off the source of refrigerant retention.

[0095] The basis for canceling the shutdown protection when the exhaust temperature is too high is: (1) When the exhaust temperature Td of the compressor is greater than or equal to the fifth set temperature (e.g., 115℃), the compressor frequency is reduced to protect the compressor; (2) The oil return control only has the sixth set duration (e.g., 2 minutes).

[0096] In this application, the first set temperature A is any value between 40℃ and 50℃, and the third set temperature E is any value between 35℃ and 40℃. However, the first set temperature A is always greater than the third set temperature E.

[0097] The second set temperature B is any value between 2℃ and 5℃, and the fourth set temperature C is any value between 5℃ and 8℃. However, the second set temperature B is always less than the fourth set temperature C.

[0098] The fifth set temperature is 115℃. The first set duration T1 is any value between 3 minutes and 6 minutes. The second set duration T2 is 2 minutes. The third set duration T3 is any value between 15 minutes and 30 minutes. The fourth set duration is any value between 15 seconds and 60 seconds. The fifth set duration is 1 hour; the sixth set duration is 2 minutes.

[0099] By using the above range, the opening and closing conditions can be accurately determined.

[0100] In some embodiments of this application, the outdoor unit includes two outdoor units connected in parallel. For example... Figure 1 As shown, the liquid pipes of the two outdoor units are connected in parallel and are connected to the liquid pipe of the indoor unit; the gas pipes of the two outdoor units are connected in parallel and are connected to the gas pipe of the indoor unit.

[0101] By designing two outdoor units connected in parallel, the indoor load requirements can be met while avoiding waste caused by an excessive number of outdoor units.

[0102] Below, in conjunction with Figure 9 , Figure 10 Explain the operating logic of the air conditioning system in detail.

[0103] In practical applications of multi-module combined air conditioning systems (including multiple parallel outdoor units and multiple parallel indoor units), taking large-space buildings such as villas as an example, when the capacity of a single outdoor unit cannot meet the cooling and heating load requirements of the entire house, it is usually necessary to use 2-3 outdoor units connected in parallel for cooling and heating. However, in actual use, a contradiction often arises between space utilization and system configuration. For example, when only 1-2 rooms are occupied, the system will operate under the low-probability design condition of "low load - multiple modules (multiple outdoor units)" for a long time. When the indoor temperature reaches the set value, it enters the temperature control shutdown state, and multiple outdoor units shut down simultaneously. The system restarts when the indoor ambient temperature rises back to the start-up threshold. To ensure unit reliability and reduce the possibility of oil or liquid accumulation in outdoor units, multiple outdoor units are started simultaneously during the initial startup process, which takes approximately 15 to 60 seconds. Once normal operating conditions are reached, the system switches to the required outdoor unit based on load demand. When an outdoor unit stops, its compressor stops, and the electronic expansion valve immediately closes. Some high-pressure refrigerant may remain in the outdoor heat exchanger of the stopped outdoor unit and not be able to be discharged. If the pressure in the stopped outdoor unit decreases after the compressor stops, and the electronic expansion valve remains open for an extended period, the refrigerant in the running outdoor unit may flow back to the stopped outdoor unit through the liquid line due to the pressure difference.

[0104] During the shutdown process, the outdoor unit undergoes a significant state change: after the compressor stops working, the outdoor heat exchanger switches from condenser (COND) mode to evaporator (evap) mode, and the electronic expansion valve (EVO) rapidly closes from its maximum opening (EVOmax) to 0PLs. This abrupt change in state causes the liquid refrigerant to be "locked" in the outdoor heat exchanger of the shutdown unit. Since the outdoor fan stops at this time, natural convection occurs on the surface of the outdoor heat exchanger, and the refrigerant will condense into liquid refrigerant over a long period of time.

[0105] More seriously, low-frequency operation under light load conditions exacerbates this problem. After the system has run continuously for more than one hour, to ensure the reliability of the compressor lubrication system, the control module will automatically trigger the oil return control program, causing the compressor operating frequency to briefly increase to above 60Hz. At this time, the circulation system experiences a sudden drop in suction pressure (usually below 0.5MPa) due to insufficient refrigerant, and the compressor's discharge temperature rapidly rises to above 115℃. In nighttime operation scenarios, if the indoor set temperature is high (e.g., 26℃), the outdoor unit will enter a frequent temperature-controlled start-stop cycle. Each start-up process will repeat the above-mentioned refrigerant distribution imbalance problem, forming a vicious cycle of "shutdown - refrigerant accumulation - start-up - refrigerant shortage - protection shutdown". Durability tests show that after 72 hours of continuous intermittent operation, the circulating refrigerant amount in the operating module can be reduced to 40% of the initial value, causing the indoor unit heat exchanger superheat (SH) to exceed 15K. The electronic expansion valve is forced to maintain an opening of more than 80% to compensate for the insufficient refrigerant, thereby generating high-frequency airflow noise (measured up to 42dB).

[0106] This refrigerant imbalance not only affects user experience but also poses a serious threat to equipment safety. Insufficient refrigerant in the outdoor unit leads to excessive superheat in the return gas, causing the compressor to operate in a "dry compression" state. When the cylinder temperature exceeds 120°C, it will cause carbonization of the lubricating oil. Furthermore, excessively high temperatures (above 85°C) in the inverter module during high-frequency operation can lead to thermal breakdown of power components. These problems are particularly pronounced in large-space buildings such as villas, where air conditioning systems typically have more than three outdoor unit modules, but the actual occupancy rate is often less than 30%, creating a typical "oversized engine for a small load" operating condition.

[0107] To address the refrigerant retention issue in multi-module air conditioning systems during low-load cooling operation, this application designs a control module for detecting whether refrigerant is retained in the shut-down outdoor unit module and implementing a control method for refrigerant discharge, which can reduce refrigerant retention in the shut-down outdoor unit.

[0108] The delayed closing strategy for the electronic expansion valve on the liquid line of the outdoor heat exchanger of the outdoor unit that is being shut down mainly includes the following steps, see [link to relevant documentation]. Figure 9 As shown.

[0109] Step S51: Determine whether it is a multi-module combined air conditioning system.

[0110] If it is a multi-module combined air conditioning system, that is, including multiple outdoor units and multiple indoor units connected in parallel, then proceed to step S52.

[0111] Step S52: Determine whether the following conditions are met: compressor frequency Ft=0, and the high pressure Pd of the outdoor unit when it is stopped is greater than or equal to the average high pressure Pdave of the outdoor unit when it is running.

[0112] If satisfied, proceed to step S53: maintain the opening of the electronic expansion valve of the outdoor unit at the time of shutdown for a fourth set duration (e.g., 15S~60S). Then proceed to step S54.

[0113] If the conditions are not met, proceed directly to step S54.

[0114] Step S54: The opening degree of the electronic expansion valve of the outdoor unit that is shut down is 0.

[0115] For outdoor units that are shut down and whose outdoor heat exchangers are in evaporator heat exchange mode, and whose high pressure is detected to be greater than or equal to the average high pressure of the operating outdoor units, the original control logic strategy of immediately closing the electronic expansion valve of the shut-down outdoor unit to 0 position to prevent refrigerant backflow is optimized to maintain the previous opening position for a certain period of time before gradually closing it.

[0116] This delayed shutdown control mechanism utilizes system residual pressure to push some of the liquid refrigerant accumulated in the heat exchanger of the shut-down outdoor unit back into the circulation system, reducing the amount of refrigerant retained in the shut-down outdoor unit and effectively alleviating the problem of insufficient refrigerant in the circulation system. Experimental data shows that it can reduce the amount of refrigerant retained during a single shutdown process by approximately 35%.

[0117] The control strategy for opening and closing the bypass valve of the outdoor unit that is shut down mainly includes the following steps, see below. Figure 10 As shown.

[0118] Step S61: Determine whether the following conditions are met: modular combination (multi-module combined air conditioning system) and cooling operation.

[0119] If satisfied, proceed to step S62.

[0120] Step S62: Determine whether the following conditions are met: In cooling mode, the superheat of the compressor discharge of the outdoor unit is Tdsh≥A, and the superheat of the outdoor heat exchanger (Tc-Te)≤B; and the time since the last opening and closing of the bypass valve of the outdoor unit is >T3.

[0121] If the conditions are met, proceed to step S63: Open the bypass valve (SVA on) of the outdoor unit that is shut down.

[0122] Step S64: Determine whether any of the following closing conditions are met: The compressor exhaust superheat Tdsh of the outdoor unit is less than E; The outdoor heat exchanger of the outdoor unit has a superheat (Tc-Te) greater than C; The low-pressure output of the outdoor unit is Ps-Ps_ini > D; The bypass valve of the outdoor unit that is shut down remains open for a duration of T1.

[0123] If satisfied, proceed to step S65: close the bypass valve (SVA off) of the outdoor unit that is shut down.

[0124] Step S66: Determine if the following condition is met: the bypass valve of the outdoor unit being shut down has been continuously closed for a duration of T2.

[0125] If satisfied, return to step S61.

[0126] Tc is the saturation temperature corresponding to the high pressure of the outdoor unit, Te is the temperature of the liquid outlet pipe of the condenser of the outdoor unit, and Ps_ini is the low pressure of the outdoor unit at the start of this control (i.e., when the bypass valve is open).

[0127] When the system is in modular cooling operation mode, the control module monitors key parameters of the operating outdoor unit in real time. If the compressor discharge superheat exceeds the temperature threshold A (A is any value within 40℃~50℃), and the outdoor heat exchanger superheat is below the temperature threshold B (B is any value within 2℃~5℃), it is determined that there is a risk of refrigerant shortage in the operating outdoor unit. At this time, the system automatically triggers the bypass adjustment mechanism, opens the bypass valve SVA of the stopped outdoor unit and maintains it for a set time T1 (T1 is any value within 3 minutes~6 minutes), so that the liquid refrigerant remaining in the heat exchanger of the stopped outdoor unit is depressurized and flashed through the high and low pressure bypass circuit, and then enters the low-pressure side of the operating outdoor unit to re-enter the circulation.

[0128] The detection logic employs a dual-parameter collaborative judgment mechanism. Temperature threshold A must always be higher than temperature threshold E (E is any value within the range of 35℃ to 40℃), and superheat threshold C (C is any value within the range of 5℃ to 8℃) must be greater than temperature threshold B, forming a reliable judgment range. When the outdoor unit exhaust temperature drops below E, the low-pressure rises to D (D is any value within the range of 0.25 MPa to 0.35 MPa), the superheat rises above C, or the bypass valve SVA remains open for T1 (T1 is any value within the range of 3 minutes to 6 minutes), the control module closes the bypass valve. To avoid system fluctuations caused by frequent adjustments, a delay judgment time T2 (usually 2 minutes) is set after the bypass valve SVA closes, after which the detection process is re-entered. To reduce the frequency of frequently entering this control strategy, the time since the last opening of the bypass valve exceeds T3 (T3 is any value within the range of 15 minutes to 30 minutes). The parameter values ​​are designed with a range to accommodate system configurations of different horsepower and different refrigerant types (R32 / R410A), and can maintain detection accuracy (±1℃) within an ambient temperature range of -5℃ to 43℃.

[0129] The air conditioning system disclosed in this application is a multi-module combined air conditioning system that can detect whether refrigerant is retained in the shut-down outdoor unit, i.e., detect whether there is a refrigerant imbalance, and can control the discharge of refrigerant from the shut-down outdoor unit. During low-load indoor use, it can reduce the retention of refrigerant in the shut-down outdoor unit.

[0130] To achieve accurate detection and adaptive adjustment of refrigerant deficiency in multi-module air conditioning systems, this application constructs an intelligent diagnostic system based on multi-parameter fusion. This application innovatively proposes a solution for improving cooling performance under low loads based on existing hardware architecture. By optimizing the control logic, it achieves: less refrigerant retention in the outdoor unit during shutdown; and accurate detection and proactive release of refrigerant after a small amount of refrigerant has accumulated.

[0131] The core improvements are reflected in two dimensions: First, the timing control of the electronic expansion valve (EVO) for module shutdown has been reconfigured, changing the traditional "immediately close the electronic expansion valve" strategy to "delay the closing mechanism by detecting the pressure difference between the shutdown and operating modules." After the compressor stops, the electronic expansion valve (EVO) remains open for a certain period of time, using the system residual pressure to push some of the retained refrigerant into the circulation system. Second, the high and low pressure bypass circuits are used as emergency adjustment channels. Temperature sensors monitor the exhaust superheat of the operating outdoor unit and the superheat of the outdoor heat exchanger in real time. When the exhaust superheat is greater than or equal to temperature threshold A, and the outdoor heat exchanger superheat is less than or equal to temperature threshold B, the bypass solenoid valve of the shut-down outdoor unit is automatically opened, allowing the liquid refrigerant retained in the heat exchanger to re-enter the circulation through pressure reduction and flash evaporation.

[0132] The significant advantage of this solution is that it does not require additional hardware costs and can achieve three major technological breakthroughs simply by upgrading the control algorithm: (1) Establish a quantitative evaluation model of refrigerant distribution status and combine parameters such as running time, indoor load rate, and number of module start-stop times to achieve accurate prediction; (2) Develop a judgment mechanism that combines time and parameters to avoid system fluctuations caused by the back-and-forth switching of bypass valves; (3) Design an adaptive learning mechanism to optimize the delayed shutdown time and bypass trigger threshold through accumulated running data to adapt to different ambient temperatures (-5℃~43℃) and load conditions.

[0133] Actual operation tests show that, under extreme conditions of continuous operation of a single indoor unit for 8 hours, using this application, the fluctuation rate of the system's circulating refrigerant volume is controlled within ±5%, the noise of the indoor unit is reduced to below 35dB, and the exhaust temperature of the compressor is stabilized in the safe range of 85℃-95℃, completely solving the reliability problem of multi-module operation under low load.

[0134] 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.

[0135] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention 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 the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An outdoor unit for air conditioning, characterized in that, include: Multiple outdoor units connected in parallel; a bypass pipeline is provided between the exhaust port and the intake port of the compressor of the outdoor unit; a bypass valve is provided on the bypass pipeline; The control module is configured as follows: Determine if the start-up conditions are met: In cooling mode, the superheat of the compressor discharge of the outdoor unit reaches the upper limit of the first set temperature, and the superheat of the outdoor heat exchanger of the outdoor unit reaches the lower limit of the second set temperature. If the opening conditions are met, the bypass valve of the outdoor unit that is shut down will be opened; After the bypass valve of the outdoor unit is opened, the bypass valve of the outdoor unit will be closed if any of the following closing conditions are met. Shutdown condition 1: The compressor exhaust superheat of the outdoor unit reaches the lower limit of the third set temperature; Shutdown condition two: The superheat of the outdoor heat exchanger of the outdoor unit reaches the upper limit of the fourth set temperature. The first set temperature is higher than the third set temperature; the second set temperature is lower than the fourth set temperature.

2. The outdoor unit of the air conditioner according to claim 1, characterized in that: The shutdown conditions also include: Closure condition 3: The low-pressure of the outdoor unit is higher than the set pressure when the bypass valve is open.

3. The outdoor unit of the air conditioner according to claim 1, characterized in that: The shutdown conditions also include: Closing condition four: The bypass valve of the outdoor unit is continuously open for the first set time.

4. The outdoor unit of the air conditioner according to claim 1, characterized in that: The control module is also configured to: After the bypass valve of the outdoor unit is closed, a second set time is delayed before determining whether the opening conditions are met.

5. The outdoor unit of the air conditioner according to claim 1, characterized in that: The opening conditions also include: the time elapsed since the last time the bypass valve of the outdoor unit was turned on or off exceeds a third preset time.

6. The outdoor unit of the air conditioner according to claim 1, characterized in that: The control module is also configured to: To determine if the outdoor unit being shut down meets the following condition: the high-pressure pressure reaches the upper limit of the average high-pressure pressure of the operating outdoor unit when it is shut down; If the conditions are met, the electronic expansion valve on the liquid pipe of the outdoor unit will remain open at the fourth set position for the fourth time before gradually closing.

7. The outdoor unit of the air conditioner according to any one of claims 1 to 6, characterized in that: The control module is also configured to: After the compressor has been running at a set low frequency for five set durations, it enters the oil return mode; in the oil return mode, the compressor is controlled to run at a set high frequency; wherein, the set high frequency is greater than the set low frequency; When the oil return time reaches the sixth preset time, exit the oil return mode.

8. The outdoor unit of the air conditioner according to claim 7, characterized in that: The control module is also configured to: In the oil return mode, when the compressor's discharge temperature reaches the upper limit of the fifth set temperature, the compressor frequency is reduced.

9. An air conditioning system, characterized in that, include: Indoor unit, which includes multiple indoor units connected in parallel; The outdoor unit is an air conditioning outdoor unit as described in any one of claims 1 to 8; The outdoor unit is connected to the indoor unit.

10. The air conditioning system according to claim 9, characterized in that: The outdoor unit comprises two outdoor units connected in parallel.

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