Multi-connected system

Abstract

The application provides a multi-connected system, which comprises a compressor, an outdoor heat exchanger, a main throttling valve and an indoor heat exchanger connected in sequence to form a closed cycle, and further comprises: an intermediate heat exchanger, a second end of a heat exchange auxiliary path is connected to a jet augmenting enthalpy port through a first branch pipeline, and the second end of the heat exchange auxiliary path is connected to a back gas port of the compressor through a second branch pipeline; a first opening adjusting valve for adjusting the amount of refrigerant entering the jet augmenting enthalpy port; a second opening adjusting valve for adjusting the amount of refrigerant entering the back gas port; and an opening control device configured to perform: adjusting the opening of the first opening adjusting valve according to the exhaust superheat degree of the compressor; and adjusting the opening of the second opening adjusting valve according to the pressure difference between the low pressure of the compressor and the set pressure. The application can ensure stable operation of the multi-connected system and improve the heating capacity of the multi-connected system.

Description

Technical Field

[0001] This invention relates to the field of air conditioning, specifically to a multi-split air conditioning system that can improve low-temperature heating capacity. Background Technology

[0002] When a multi-split system is operating at low temperatures for heating, the outdoor unit's heat exchange efficiency is also low due to the low outdoor ambient temperature. At the same time, since the indoor unit has a larger internal volume during heating, the refrigerant circulation volume needs to be increased to improve the heat exchange effect of the indoor unit, which increases the heat exchange burden on the outdoor heat exchanger.

[0003] Currently, the low-temperature heating capacity of multi-split air conditioning systems is mainly improved by increasing the area of ​​outdoor heat exchangers and using vapor injection enthalpy-enhancing compressors. However, larger heat exchanger areas increase material costs for manufacturers, while the control of vapor injection enthalpy-enhancing compressors is relatively simple, making it difficult to guarantee compressor efficiency. Summary of the Invention

[0004] To address the above problems, this invention provides a multi-split air conditioning system. By diverting the refrigerant entering the outdoor heat exchanger, the heat exchange efficiency and effect of the outdoor heat exchanger are ensured. Furthermore, the amount of refrigerant entering the compressor's jet enthalpy inlet is precisely adjusted based on the exhaust superheat, and the amount of refrigerant entering the compressor's return gas inlet is precisely adjusted based on the difference between the low-pressure and set pressure. This ensures stable operation of the multi-split air conditioning system while improving its heating capacity.

[0005] This invention provides a multi-split air conditioning system, comprising a compressor, an outdoor heat exchanger, a main throttling valve, and an indoor heat exchanger connected in sequence to form a closed loop. The compressor has a jet enthalpy-increasing port and a return gas port. The multi-split air conditioning system further includes:

[0006] The intermediate heat exchanger includes a main heat exchange circuit and an auxiliary heat exchange circuit. The first end of the main heat exchange circuit is connected to the indoor heat exchanger, and the second end of the main heat exchange circuit is connected to the main throttle valve. The first end of the auxiliary heat exchange circuit is connected between the indoor heat exchanger and the first end of the main heat exchange circuit through a connecting pipe. The second end of the auxiliary heat exchange circuit is connected to the jet enthalpy inlet through a first branch pipe, and the second end of the auxiliary heat exchange circuit is connected to the compressor return port through a second branch pipe.

[0007] The first opening regulating valve is located in the first branch pipeline and is used to regulate the amount of refrigerant entering the jet enthalpy-increasing port;

[0008] The second opening regulating valve is located in the second branch pipeline and is used to regulate the amount of refrigerant entering the return gas port.

[0009] The opening control device is configured to perform:

[0010] First opening adjustment step: Adjust the opening of the first opening adjustment valve according to the superheat of the compressor's exhaust;

[0011] Second opening adjustment step: Adjust the opening of the second opening adjustment valve according to the pressure difference between the compressor's low pressure and the set pressure.

[0012] According to this technical solution, adjusting the opening of the second regulating valve based on the pressure difference between the low-pressure and the set pressure, i.e., adjusting the amount of refrigerant entering the compressor's return port, allows the compressor's low-pressure and return gas volume to be controlled within a reasonable range. This improves the accuracy of refrigerant control and increases the compressor's power, thereby increasing the heating capacity of the multi-split system and ensuring heating performance. Furthermore, adjusting the compressor's vapor injection enthalpy based on the exhaust superheat increases the compressor's compression efficiency, further enhancing the multi-split system's heating capacity. Adjusting the opening of the first regulating valve improves the accuracy of vapor injection enthalpy, maintaining the exhaust superheat within a reasonable range. This prevents compressor damage due to excessively high exhaust superheat and liquid slugging due to excessively low exhaust superheat, extending compressor lifespan and ensuring system reliability while improving the multi-split system's heating capacity. Simultaneously adjusting the compressor's vapor injection enthalpy and return gas volume ensures a more uniform refrigerant flow into the compressor, improving compressor efficiency. In addition, in this embodiment, when heating at low temperatures, the refrigerant is diverted to return directly to the compressor without passing through the outdoor heat exchanger, which reduces the load on the outdoor heat exchanger, helps to improve the heat exchange efficiency and heat exchange capacity of the outdoor heat exchanger, reduces the occurrence of frost on the outdoor heat exchanger, and ensures the heating effect at low temperatures.

[0013] In an optional technical solution of the present invention, in the first opening adjustment step,

[0014] If the exhaust superheat is less than the first superheat preset value, the first opening regulating valve will be closed and the second opening regulating valve will be forcibly opened to the maximum opening.

[0015] If the exhaust superheat is not less than the first superheat preset value and less than the second superheat preset value, then control the opening of the first opening regulating valve to be reduced by the first opening degree.

[0016] If the exhaust superheat is not less than the second superheat preset value and less than the third superheat preset value, then the opening of the first opening regulating valve is increased by the second opening.

[0017] If the exhaust superheat is not less than the third superheat preset value, then the opening of the first opening regulating valve is increased by the third opening.

[0018] The first, second, and third superheat preset values ​​increase sequentially, and the second opening is smaller than the third opening.

[0019] According to the technical solution, when the exhaust superheat is lower than the first preset value of superheat or greater than the first preset value of superheat but less than the second preset value of superheat, the first opening regulating valve is closed or reduced to decrease the amount of refrigerant entering the jet enthalpy-increasing port. This helps to increase the amount of refrigerant in the main circuit, increase the exhaust superheat of the compressor, and prevent the compressor from being subjected to liquid slugging.

[0020] Furthermore, with the first opening regulating valve in the closed state, the second opening regulating valve is forcibly opened to the maximum opening degree to prevent the liquid refrigerant at the outlet of the indoor heat exchanger from returning to the compressor through the outdoor heat exchanger and causing liquid slugging in the compressor. This allows the refrigerant at the outlet of the intermediate heat exchanger to return to the compressor after being throttled and vaporized by the second opening regulating valve, thus achieving gas replenishment to the compressor, which is beneficial to improving the compressor's power and heating capacity.

[0021] When the exhaust superheat exceeds the second superheat preset value, the opening of the second opening regulating valve is increased, allowing more refrigerant to return to the compressor after being throttled by the second opening regulating valve. This increases the compressor's power and the heating capacity of the multi-split system, improving the heating effect. It also reduces the load on the outdoor heat exchanger, ensuring the heat exchange efficiency and effect of the outdoor heat exchanger.

[0022] In an optional technical solution of the present invention, in the second opening adjustment step,

[0023] If the pressure difference is greater than the first preset pressure value, the second opening regulating valve will be closed.

[0024] If the pressure difference is not greater than the first preset pressure value but is greater than the second preset pressure value, then the opening of the second opening regulating valve is increased by the fourth opening degree.

[0025] If the pressure difference is less than the second pressure preset value, the opening of the second opening regulating valve will be increased by the fifth opening degree.

[0026] If the pressure difference is less than the third preset pressure value, then control the second opening regulating valve to the maximum opening.

[0027] The first, second, and third pressure preset values ​​decrease sequentially, and the fourth opening is smaller than the fifth opening.

[0028] According to this technical solution, as the pressure difference between the low-pressure and the set pressure increases, the opening of the second opening regulating valve gradually decreases until it closes, indicating that the low-pressure is relatively high. When the pressure difference is large, the second opening regulating valve is closed; when the pressure difference is small, the opening of the second opening regulating valve is increased. This allows more refrigerant from the heat exchange auxiliary circuit outlet to flow into the compressor's return port and / or the compressor's vapor injection enthalpy inlet, increasing the compressor's return pressure and preventing frost formation on the outdoor heat exchanger under low-pressure conditions. When the pressure difference is less than the third preset pressure value, adjusting the opening of the second opening regulating valve to its maximum allows the refrigerant from the heat exchange auxiliary circuit outlet to enter the compressor more quickly, increasing the return pressure.

[0029] In an optional technical solution of the present invention, the set pressure is positively correlated with the outdoor ambient temperature.

[0030] According to this technical solution, the set pressure is higher when the outdoor ambient temperature is high and lower when the outdoor ambient temperature is low. The set pressure is determined based on the outdoor ambient temperature, which improves the accuracy of the opening adjustment of the second opening regulating valve.

[0031] In the optional technical solution of the present invention, a third opening regulating valve is provided in the connecting pipeline for regulating the amount of refrigerant entering the heat exchange auxiliary circuit.

[0032] The opening control device is configured to perform:

[0033] The third opening adjustment step: Adjust the opening of the third opening regulating valve according to the temperature difference between the first end and the second end of the heat exchange auxiliary circuit.

[0034] According to this technical solution, by setting a third opening regulating valve, the refrigerant at the outlet of the indoor heat exchanger can be easily diverted, adjusting the refrigerant content entering the outdoor heat exchanger from the indoor heat exchanger outlet and the refrigerant content returning to the compressor from the indoor heat exchanger outlet. This ensures that the refrigerant entering the outdoor heat exchanger is within a reasonable range during low-temperature heating, thereby improving the heat exchange efficiency of the outdoor heat exchanger. Simultaneously, the refrigerant at the outlet of the indoor heat exchanger enters the compressor after heat exchange in the auxiliary heat exchange circuit and through either the first or second opening regulating valve, increasing the compressor's heating capacity and improving the heating effect. Adjusting the opening of the third opening regulating valve based on the temperature difference between the first and second ends of the auxiliary heat exchange circuit improves the accuracy and flexibility of the valve's opening adjustment, enhancing the reliability of the multi-split system under different operating conditions.

[0035] In an optional technical solution of the present invention, in the third opening adjustment step,

[0036] If the temperature difference is less than the first preset temperature difference value, then the opening of the third opening regulating valve will be reduced.

[0037] If the temperature difference is not less than the first preset temperature difference value and not greater than the second preset temperature difference value, then the opening of the third opening regulating valve remains unchanged.

[0038] If the temperature difference is greater than the second preset temperature difference value, the opening of the third opening regulating valve is increased; wherein, the first preset temperature difference value is less than the second preset temperature difference value;

[0039] The control device is configured to execute the first opening adjustment step and the second opening adjustment step when the opening of the third opening adjustment valve remains unchanged or the opening of the third opening adjustment valve increases.

[0040] According to this technical solution, a larger temperature difference indicates that the refrigerant temperature at the outlet of the auxiliary heat exchange circuit is relatively high, making it less likely to cause liquid slugging in the compressor. Therefore, increasing the opening of the third opening regulating valve helps to allow more refrigerant to flow into the compressor, ensuring the heating effect of the multi-split system, while reducing the load on the outdoor heat exchanger and improving its evaporation capacity and effect. Furthermore, executing the first and second opening regulation steps when the opening of the third opening regulating valve remains unchanged or increases helps to maintain the refrigerant quantity in the main circuit circulation, ensuring the heating effect of the multi-split system.

[0041] In an optional technical solution of the present invention, if the third opening regulating valve is in a holding state and the first opening regulating valve and the second opening regulating valve are in a fully open state, the third opening regulating valve is forcibly opened to the maximum opening.

[0042] According to the technical solution, when both the first and second opening regulating valves are in the fully open state, the third opening regulating valve is forcibly opened to the maximum opening degree, so that the refrigerant at the outlet of the indoor heat exchanger enters the outdoor unit to participate in the heating cycle or returns to the compressor at the maximum flow rate, which is beneficial to improve the circulation efficiency of the multi-split system and improve the low-temperature heating capacity of the multi-split system.

[0043] In an optional embodiment of the present invention, the opening control device is configured to perform:

[0044] Fourth opening adjustment step: Adjust the opening of the main throttle valve according to the difference between the outdoor ambient temperature and the outdoor coil temperature.

[0045] According to this technical solution, adjusting the opening of the main throttle valve based on the difference between the outdoor ambient temperature and the outdoor coil temperature helps to ensure that the amount of refrigerant in the main circuit is within a suitable range, enhances the heat exchange capacity of the outdoor heat exchanger, and improves the heating effect of the multi-split system.

[0046] In an optional technical solution of the present invention, in the fourth opening adjustment step,

[0047] If the difference between the outdoor ambient temperature and the outdoor coil temperature is less than the first temperature threshold, then the opening of the main throttle valve will be reduced.

[0048] If the difference between the outdoor ambient temperature and the outdoor coil temperature is greater than the second temperature threshold, then the opening of the main throttle valve will be increased.

[0049] If the difference between the outdoor ambient temperature and the outdoor coil temperature is not less than the first temperature threshold and not greater than the second temperature threshold, then the opening of the main throttle valve is maintained; wherein the first temperature threshold is less than the second temperature threshold.

[0050] According to this technical solution, a large difference between the outdoor ambient temperature and the outdoor coil temperature indicates a strong evaporation capacity of the outdoor heat exchanger. Increasing the opening of the main throttle valve allows more refrigerant to evaporate in the outdoor heat exchanger, which helps increase the heat exchange capacity of the outdoor heat exchanger and the amount of refrigerant participating in the low-temperature heating cycle, thus improving the heating effect. Conversely, a small difference between the outdoor ambient temperature and the outdoor coil temperature indicates a poor heat exchange capacity of the outdoor heat exchanger. Closing the opening of the main throttle valve prevents more refrigerant from depositing in the outdoor heat exchanger, ensuring that the heat exchange capacity of the outdoor heat exchanger matches the amount of refrigerant, thereby improving the heat exchange capacity and efficiency. When the difference between the outdoor ambient temperature and the outdoor coil temperature is within a suitable range, maintaining the opening of the main throttle valve avoids frequent adjustments and ensures the stable operation of the multi-split system. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the structure of a multi-unit system according to an embodiment of the present invention.

[0052] Figure 2 This is a schematic diagram of the operation process of the multi-unit system in an embodiment of the present invention.

[0053] Figure 3 This is a schematic diagram of the opening control of the first and second opening control valves in a multi-split air conditioning system under the embodiment of the present invention, when the opening of the third opening control valve remains unchanged.

[0054] Figure 4 This is a schematic diagram of the opening control of the first and second opening control valves in a multi-split air conditioning system when the third opening control valve is increased, according to an embodiment of the present invention.

[0055] Figure label:

[0056] Compressor 11; Injection enthalpy inlet 111; Return gas inlet 112; Outdoor heat exchanger 12; Main throttle valve 13; Indoor heat exchanger 14; Intermediate heat exchanger 15; Main heat exchange line 151; Auxiliary heat exchange line 152; Four-way valve 16; Gas-liquid separator 17; Connecting pipeline L0; First branch pipeline L1; Second branch pipeline L2; First opening regulating valve EXVE; Second opening regulating valve EXVD; Third opening regulating valve EXVC. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] like Figure 1 , Figure 2 As shown, the present invention provides a multi-split air conditioning system, including a compressor 11, an outdoor heat exchanger 12, a main throttle valve 13, and an indoor heat exchanger 14 connected in sequence to form a closed loop. The compressor 11 has a jet enthalpy-increasing port 111 and a return gas port 112. The multi-split air conditioning system also includes an intermediate heat exchanger 15, a first opening degree regulating valve EXVE, a second opening degree regulating valve EXVD, and an opening degree control device (not shown in the figure).

[0059] Specifically, the intermediate heat exchanger 15 includes a main heat exchange path 151 and an auxiliary heat exchange path 152. The first end of the main heat exchange path 151 is connected to the indoor heat exchanger 14, and the second end of the main heat exchange path 151 is connected to the main throttle valve 13. The first end of the auxiliary heat exchange path 152 is connected between the indoor heat exchanger 14 and the first end of the main heat exchange path 151 through a connecting pipe L0. The second end of the auxiliary heat exchange path 152 is connected to the jet enthalpy-increasing port 111 through a first branch pipe L1, and the second end of the auxiliary heat exchange path 152 is connected to the return gas port 112 of the compressor 11 through a second branch pipe L2.

[0060] The first opening regulating valve EXVE is located in the first branch line L1 and is used to regulate the amount of refrigerant entering the jet enthalpy-increasing port 111. The second opening regulating valve EXVD is located in the second branch line L2 and is used to regulate the amount of refrigerant entering the return port 112. The opening control device is configured to perform:

[0061] First opening adjustment step: Adjust the opening of the first opening adjustment valve EXVE according to the discharge superheat of compressor 11 (the difference between discharge temperature Tp and high pressure Pc (i.e., discharge pressure, which can be obtained by the high pressure sensor installed in the discharge pipeline of compressor 11) and the corresponding saturation temperature Tc).

[0062] Second opening adjustment step: Adjust the opening of the second opening adjustment valve EXVD according to the pressure difference between the low pressure of compressor 11 (denoted as Pe, which can be obtained by the low pressure sensor located in the return gas line of compressor 11) and the set pressure (denoted as Pes).

[0063] By adjusting the opening of the second opening regulating valve EXVD according to the pressure difference between the low pressure (the return gas pressure of compressor 11) and the set pressure, the amount of refrigerant entering the return gas port 112 of compressor 11 is adjusted. This not only keeps the low pressure and return gas volume of compressor 11 within a reasonable range, improving the accuracy of refrigerant control, but also increases the power of compressor 11, thereby increasing the heating capacity of the multi-split system and ensuring the heating effect.

[0064] Furthermore, by adjusting the enthalpy injection rate of compressor 11 based on the exhaust superheat, the compression efficiency of compressor 11 is increased, thereby improving the heating capacity of the multi-split system. Additionally, by adjusting the opening of the first opening regulating valve EXVE, the accuracy of the enthalpy injection is improved, ensuring that the exhaust superheat is maintained within a reasonable range. This prevents compressor 11 damage due to excessively high exhaust superheat and liquid slugging due to excessively low exhaust superheat, thus extending the service life of compressor 11. This ensures system reliability while improving the heating capacity of the multi-split system. By simultaneously adjusting the enthalpy injection rate and return gas flow rate of compressor 11, the refrigerant entering compressor 11 is kept in a more uniform state, improving compressor efficiency.

[0065] In addition, in this embodiment, when heating at low temperatures, the refrigerant is diverted to return directly to the compressor 11 without passing through the outdoor heat exchanger 12, which reduces the load on the outdoor heat exchanger 12, helps to improve the heat exchange efficiency and heat exchange capacity of the outdoor heat exchanger 12, reduces the occurrence of frost on the outdoor heat exchanger 12, and ensures the heating effect at low temperatures.

[0066] It should be noted that in some embodiments, the multi-split air conditioning system may also include an oil separator 16, a gas-liquid separator 17, and a four-way valve 16. The connection relationship between the gas-liquid separator 17 and the four-way valve 16 is shown in the figure and will not be repeated here. In addition, the indoor heat exchanger 14 may include multiple units arranged in parallel, which is not limited in this embodiment. The main circuit refers to the circuit including the compressor 11, the indoor heat exchanger 14, the intermediate heat exchanger 15, the main throttle valve 13, and the outdoor heat exchanger 12. The auxiliary circuit refers to the circuit including the heat exchange auxiliary circuit 152.

[0067] The opening degree control device can be an integrated circuit chip with signal processing capabilities. The aforementioned opening degree control device can be a general-purpose processor, including a central processing unit (CPU), or a microcontroller, microcontroller unit (MCU), complex programmable logic device (CPLD), field-programmable gate array (FPGA), application-specific integrated circuit (ASIC), embedded ARM, etc. The opening degree control device can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this invention.

[0068] In a preferred embodiment of the present invention, in the first opening adjustment step,

[0069] If the exhaust superheat is less than the first superheat preset value, the first opening regulating valve EXVE will be closed and the second opening regulating valve EXVD will be forcibly opened to the maximum opening.

[0070] If the exhaust superheat is not less than the first superheat preset value and less than the second superheat preset value, then control the opening of the first opening regulating valve EXVE to be reduced by the first opening degree.

[0071] If the exhaust superheat is not less than the second superheat preset value and less than the third superheat preset value, then the opening of the first opening regulating valve EXVE is increased by the second opening degree.

[0072] If the exhaust superheat is not less than the third superheat preset value, then the opening of the first opening regulating valve EXVE is increased by the third opening degree.

[0073] The first, second, and third superheat preset values ​​increase sequentially, and the second opening is smaller than the third opening.

[0074] In this way, when the exhaust superheat is lower than the first preset superheat value or higher than the first preset superheat value but lower than the second preset superheat value, the first opening regulating valve EXVE is closed or partially closed, reducing the amount of refrigerant entering the jet enthalpy-increasing port 111. This helps to increase the amount of refrigerant in the main circulation, increase the exhaust superheat of the compressor 11, and prevent the compressor 11 from being subjected to liquid slugging. Furthermore, with the first opening regulating valve EXVE in the closed state, the second opening regulating valve EXVD is forcibly opened to its maximum opening, allowing the liquid refrigerant at the outlet of the intermediate heat exchanger 15 to return to the compressor 11 after being throttled by the second opening regulating valve EXVD and separated by the gas-liquid separator 17. This achieves gas replenishment to the compressor 11, which helps to increase the power of the compressor 11 and increase its heating capacity.

[0075] When the exhaust superheat is greater than the second superheat preset value, the opening of the second opening regulating valve EXVD is increased, so that more refrigerant returns to the compressor 11 after being throttled by the second opening regulating valve EXVD, thereby increasing the power of the compressor 11 and the heating capacity of the multi-split system, and improving the heating effect; and reducing the load on the outdoor heat exchanger 12, ensuring the heat exchange efficiency and heat exchange effect of the outdoor heat exchanger 12.

[0076] In a preferred embodiment of the present invention, in the second opening adjustment step,

[0077] If the pressure difference is greater than the first preset pressure value, then the second opening regulating valve EXVD will be closed.

[0078] If the pressure difference is not greater than the first preset pressure value but is greater than the second preset pressure value, then the opening of the second opening regulating valve EXVD is increased by the fourth opening degree.

[0079] If the pressure difference is less than the second pressure preset value, the opening of the second opening regulating valve EXVD is increased by the fifth opening degree.

[0080] If the pressure difference is less than the third pressure preset value, then control the second opening regulating valve EXVD to the maximum opening.

[0081] The first, second, and third pressure preset values ​​decrease sequentially, and the fourth opening is smaller than the fifth opening.

[0082] In this way, as the pressure difference between the low-pressure and the set pressure increases, the opening of the second opening regulating valve EXVD gradually decreases until it closes, indicating that the low-pressure is high. When the pressure difference is large, closing the second opening regulating valve EXVD and opening it wider when the pressure difference is small allows more refrigerant from the outlet of the heat exchange auxiliary circuit 152 to flow into the return port 112 and / or the injection enthalpy-increasing port 111 of the compressor 11, increasing the return gas pressure of the compressor 11 and preventing frost formation on the outdoor heat exchanger under low-pressure conditions. When the pressure difference is less than the third preset pressure value, adjusting the opening of the second opening regulating valve EXVD to its maximum allows the refrigerant from the outlet of the heat exchange auxiliary circuit 152 to enter the compressor 11 more quickly, increasing the return gas pressure.

[0083] In a preferred embodiment of the present invention, the set pressure is positively correlated with the outdoor ambient temperature.

[0084] By using the above method, the set pressure is higher when the outdoor ambient temperature is high and lower when the outdoor ambient temperature is low. The set pressure is determined according to the outdoor ambient temperature, which improves the accuracy of the opening adjustment of the second opening regulating valve EXVD.

[0085] In a preferred embodiment of the present invention, a third opening regulating valve EXVC is further included, which is located in the connecting pipeline L0 and is used to regulate the amount of refrigerant entering the heat exchange auxiliary pipeline 152.

[0086] The opening control device is configured to perform:

[0087] The third opening adjustment step: Adjust the opening of the third opening regulating valve EXVC according to the temperature difference between the first end and the second end of the heat exchange auxiliary circuit 152 (as shown by the temperature difference between the two temperature sensors T6B and T6A in the figure).

[0088] In this embodiment, by setting a third opening regulating valve EXVC, the refrigerant at the outlet of the indoor heat exchanger 14 can be diverted, adjusting the refrigerant content entering the outdoor heat exchanger 12 from the outlet of the indoor heat exchanger 14 and the refrigerant content returning to the compressor 11 from the outlet of the indoor heat exchanger 14. This ensures that the refrigerant entering the outdoor heat exchanger 12 is within a reasonable range during low-temperature heating, thereby improving the heat exchange efficiency of the outdoor heat exchanger 12. Simultaneously, the refrigerant at the outlet of the indoor heat exchanger 14 undergoes heat exchange via the heat exchange auxiliary circuit 152 and enters the compressor 11 via the first opening regulating valve EXVE or the second opening regulating valve EXVD, increasing the heating capacity of the compressor 11 and improving the heating effect. Adjusting the opening of the third opening regulating valve EXVC based on the temperature difference between the first and second ends of the heat exchange auxiliary circuit 152 improves the accuracy and flexibility of the EXVC opening adjustment, enhancing the reliability of the multi-split system under different operating conditions.

[0089] In a preferred embodiment of the present invention, in the third opening adjustment step,

[0090] If the temperature difference is less than the first preset temperature difference value, then control the opening of the third opening regulating valve EXVC to be reduced.

[0091] If the temperature difference is not less than the first preset temperature difference value and not greater than the second preset temperature difference value, then the opening of the third opening regulating valve EXVC remains unchanged.

[0092] If the temperature difference is greater than the second preset temperature difference value, the opening of the third opening regulating valve EXVC is increased; wherein, the first preset temperature difference value is less than the second preset temperature difference value.

[0093] The control device is configured to execute the first opening adjustment step and the second opening adjustment step when the opening of the third opening adjustment valve EXVC remains unchanged or the opening of the third opening adjustment valve EXVC increases.

[0094] As described above, a larger temperature difference indicates that the refrigerant temperature at the outlet of the auxiliary heat exchange circuit 152 is relatively high, making it less likely to cause liquid slugging in the compressor 11. Therefore, increasing the opening of the third opening regulating valve EXVC allows more refrigerant to flow into the compressor 11, ensuring the heating effect of the multi-split system. Simultaneously, it reduces the load on the outdoor heat exchanger 12, improving its evaporation capacity and efficiency. Furthermore, executing the first and second opening regulation steps when the opening of the third opening regulating valve EXVC remains unchanged or increases helps maintain the refrigerant quantity in the main circuit circulation, ensuring the heating effect of the multi-split system.

[0095] In a preferred embodiment of the present invention, if the third opening regulating valve EXVC is in a holding state and the first opening regulating valve EXVE and the second opening regulating valve EXVD are in a fully open state, the third opening regulating valve EXVC is forcibly opened to the maximum opening.

[0096] In the above manner, when the first opening regulating valve EXVE and the second opening regulating valve EXVD are both in the fully open state, the third opening regulating valve EXVC is forcibly opened to the maximum opening degree, so that the refrigerant at the outlet of the indoor heat exchanger 14 enters the outdoor unit to participate in the heating cycle or returns to the compressor 11 at the maximum flow rate, which is beneficial to improve the circulation efficiency of the multi-split system and improve the low-temperature heating capacity of the multi-split system.

[0097] In a preferred embodiment of the present invention, the opening control device is configured to perform:

[0098] Fourth opening adjustment step: Adjust the opening of the main throttle valve 13 according to the difference between the outdoor ambient temperature T4 and the outdoor coil temperature T3. Adjusting the opening of the main throttle valve 13 according to the difference between the outdoor ambient temperature T4 and the outdoor coil temperature T3 helps to ensure that the amount of refrigerant in the main circuit is within a suitable range, enhances the heat exchange capacity of the outdoor heat exchanger 12, and improves the heating effect of the multi-split system.

[0099] In a preferred embodiment of the present invention, in the fourth opening adjustment step,

[0100] If the difference between the outdoor ambient temperature T4 and the outdoor coil temperature T3 is less than the first temperature threshold, then the opening of the main throttle valve 13 will be reduced.

[0101] If the difference between the outdoor ambient temperature T4 and the outdoor coil temperature T3 is greater than the second temperature threshold, then the opening of the main throttle valve 13 will be increased.

[0102] If the difference between the outdoor ambient temperature T4 and the outdoor coil temperature T3 is not less than the first temperature threshold and not greater than the second temperature threshold, then the opening of the main throttle valve 13 is maintained; wherein the first temperature threshold is less than the second temperature threshold.

[0103] Using the above methods, when the difference between the outdoor ambient temperature T4 and the outdoor coil temperature T3 is large, it indicates that the evaporation capacity of the outdoor heat exchanger 12 is strong. Increasing the opening of the main throttle valve 13 allows more refrigerant to evaporate in the outdoor heat exchanger 12, which is beneficial for increasing the heat exchange capacity of the outdoor heat exchanger 12 and the amount of refrigerant participating in the low-temperature heating cycle, thus improving the heating effect. When the difference between the outdoor ambient temperature T4 and the outdoor coil temperature T3 is small, it indicates that the heat exchange capacity of the outdoor heat exchanger 12 is poor. Closing the opening of the main throttle valve 13 prevents more refrigerant from depositing in the outdoor heat exchanger 12, ensuring that the heat exchange capacity of the outdoor heat exchanger 12 matches the amount of refrigerant, thus improving the heat exchange capacity and efficiency of the heat exchanger. When the difference between the outdoor ambient temperature T4 and the outdoor coil temperature T3 is within a suitable range, maintaining the opening of the main throttle valve 13 can avoid frequent adjustments to the opening of the main throttle valve 13, ensuring the stable operation of the multi-split system.

[0104] In this embodiment, the temperature difference, superheat difference, and pressure difference are detected at predetermined intervals to adjust the opening of the corresponding regulating valve according to the actual temperature difference, superheat difference, and pressure difference, thereby improving the accuracy of the multi-split system control and ensuring the stable and reliable operation of the multi-split system.

[0105] The following combination Figure 2 , Figure 3 , Figure 4 The following example illustrates the specific adjustment methods of the first to third opening adjustment valves (EXVE, EXVD, EXVC) and the main throttle valve 13 in this embodiment.

[0106] The opening control logic of the third opening regulating valve EXVC is as follows:

[0107] 1. When T6B-T6A < 5℃, the third opening regulating valve EXVC is closed by 10P, and the judgment is made every 2 minutes.

[0108] 2. When 5≤T6B-T6A≤10℃, the opening of the third opening regulating valve EXVC remains unchanged.

[0109] 3. When T6B-T6A>10℃, the third opening regulating valve EXVC opens 10P, and is judged every 2 minutes; that is, the third opening regulating valve EXVC is in the open range.

[0110] II. When the third opening control valve EXVC is in the range of maintaining constant or wide opening, the opening control logic of the first opening control valve EXVE is as follows:

[0111] 1. When Tp-Tc < 8℃, the first opening regulating valve EXVE is closed, and the check is performed every 2 minutes;

[0112] 2. When 8≤Tp-Tc<10℃, the first opening regulating valve EXVE is closed by 10P, and the check is performed every 2 minutes;

[0113] 3. When 10≤Tp-Tc<20℃, the first opening regulating valve EXVE opens 10P, and is checked every 2 minutes;

[0114] 4. When Tp-Tc≥20℃, the first opening regulating valve EXVE opens 20P, and is checked every 2 minutes;

[0115] 5. The opening range of the first opening regulating valve EXVE is 0~480P.

[0116] III. When the third opening control valve EXVC is in the range of maintaining constant or wide opening, the opening control logic of the second opening control valve EXVD is as follows:

[0117] 1. When Pe-Pes > 0 MPa, the second opening regulating valve EXVD is closed, and the check is performed every 2 minutes.

[0118] 2. When -0.1MPa≤Pe-Pes≤0 degrees, the opening of the second opening regulating valve EXVD is increased by 5P, and the judgment is made every 2 minutes.

[0119] 3. When Pe-Pes < -0.1MPa, the opening of the second opening regulating valve EXVD is increased by 10P, and the judgment is made every 2 minutes.

[0120] 4. When Pe-Pes < -1.0MPa, the second opening regulating valve EXVD is forced to open to the maximum opening.

[0121] The opening range of the second opening regulating valve EXVD is 0 to 200P.

[0122] IV. The opening control logic of the main throttle valve 13 is as follows:

[0123] 1. When 3℃≤T4-T3≤5℃, the opening degree of the main throttle valve 13 remains unchanged.

[0124] 2. When T4-T3 < 3℃, the opening of the main throttle valve 13 is reduced by 5P, and the judgment is made every 2 minutes.

[0125] 3. When T4-T3>5℃, the opening of the main throttle valve 13 is increased by 5P, and the judgment is made every 2 minutes.

[0126] It should be noted that technicians can set the number of steps for opening or closing each of the above valves, as well as the preset values ​​for pressure difference, superheat difference, temperature difference, set pressure, etc., according to the actual working conditions. This invention does not limit these settings.

[0127] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-split air conditioning system, comprising a compressor, an outdoor heat exchanger, a main expansion valve, and an indoor heat exchanger connected in sequence to form a closed loop, characterized in that, The compressor has a jet enthalpy-increasing port and a return gas port, and the multi-split system also includes: An intermediate heat exchanger includes a main heat exchange path and an auxiliary heat exchange path. The first end of the main heat exchange path is connected to the indoor heat exchanger, and the second end of the main heat exchange path is connected to the main throttle valve. The first end of the auxiliary heat exchange path is connected between the indoor heat exchanger and the first end of the main heat exchange path via a connecting pipe. The second end of the auxiliary heat exchange path is connected to the vapor injection port via a first branch pipe, and the second end of the auxiliary heat exchange path is connected to the return gas port of the compressor via a second branch pipe. The first opening regulating valve is located in the first branch pipeline and is used to regulate the amount of refrigerant entering the jet enthalpy-increasing port; The second opening regulating valve is located in the second branch pipeline and is used to regulate the amount of refrigerant entering the return gas port; The opening control device is configured to perform: First opening adjustment step: Adjust the opening of the first opening adjustment valve according to the exhaust superheat of the compressor; Second opening adjustment step: Adjust the opening of the second opening adjustment valve according to the pressure difference between the low pressure of the compressor and the set pressure; In the first opening adjustment step If the exhaust superheat is less than the first superheat preset value, then the first opening adjustment valve is closed and the second opening adjustment valve is forcibly opened to the maximum opening. If the exhaust superheat is not less than the first superheat preset value and less than the second superheat preset value, then the opening of the first opening regulating valve is controlled to be reduced by the first opening degree. If the exhaust superheat is not less than the second superheat preset value and less than the third superheat preset value, then the opening of the first opening regulating valve is increased by the second opening degree. If the exhaust superheat is not less than the third superheat preset value, then the opening of the first opening regulating valve is increased by the third opening degree. The first superheat preset value, the second superheat preset value, and the third superheat preset value increase sequentially, and the second opening degree is smaller than the third opening degree; In the second opening adjustment step If the pressure difference is greater than the first preset pressure value, then the second opening regulating valve is closed. If the pressure difference is not greater than the first pressure preset value but is greater than the second pressure preset value, then the opening of the second opening regulating valve is increased by the fourth opening degree. If the pressure difference is less than the second pressure preset value, the opening of the second opening regulating valve is increased by the fifth opening degree. If the pressure difference is less than the third preset pressure value, then the second opening regulating valve is controlled to the maximum opening. The first pressure preset value, the second pressure preset value, and the third pressure preset value decrease sequentially, and the fourth opening degree is smaller than the fifth opening degree.

2. The multi-unit air conditioning system according to claim 1, characterized in that, The set pressure is positively correlated with the outdoor ambient temperature.

3. The multi-unit air conditioning system according to claim 1 or 2, characterized in that, It also includes: a third opening regulating valve, located in the connecting pipeline, used to regulate the amount of refrigerant entering the heat exchange auxiliary circuit; The opening control device is configured to perform: The third opening adjustment step: Adjust the opening of the third opening adjustment valve according to the temperature difference between the first end and the second end of the heat exchange auxiliary circuit.

4. The multi-unit air conditioning system according to claim 3, characterized in that, In the third opening adjustment step, If the temperature difference is less than the first preset temperature difference value, then the opening of the third opening regulating valve is reduced. If the temperature difference is not less than the first preset temperature difference value and not greater than the second preset temperature difference value, then the opening of the third opening regulating valve remains unchanged. If the temperature difference is greater than the second preset temperature difference value, then the opening of the third opening regulating valve is increased; wherein, the first preset temperature difference value is less than the second preset temperature difference value; The control device is configured to execute the first opening adjustment step and the second opening adjustment step when the opening of the third opening adjustment valve remains unchanged or the opening of the third opening adjustment valve increases.

5. The multi-unit air conditioning system according to claim 4, characterized in that, If the third opening regulating valve is in the holding state, and the first opening regulating valve and the second opening regulating valve are in the fully open state, the third opening regulating valve is forcibly opened to the maximum opening.

6. The multi-unit air conditioning system according to claim 5, characterized in that, The opening control device is configured to perform: Fourth opening adjustment step: Adjust the opening of the main throttle valve according to the difference between the outdoor ambient temperature and the outdoor coil temperature.

7. The multi-unit air conditioning system according to claim 6, characterized in that, In the fourth opening adjustment step, If the difference between the outdoor ambient temperature and the outdoor coil temperature is less than the first temperature threshold, then the opening of the main throttle valve is reduced. If the difference between the outdoor ambient temperature and the outdoor coil temperature is greater than the second temperature threshold, then the opening of the main throttle valve is increased. If the difference between the outdoor ambient temperature and the outdoor coil temperature is not less than the first temperature threshold and not greater than the second temperature threshold, then the opening of the main throttle valve is maintained; wherein the first temperature threshold is less than the second temperature threshold.

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