Three-pipe type multi-split air conditioner system and control method

Abstract

The invention provides a three-pipe type multi-split air conditioner system and a control method, and the three-pipe type multi-split air conditioner system comprises a high-pressure air pipe electromagnetic valve which is used for controlling opening and closing of a high-pressure air pipe; the main air pipe switching bypass pipe provides a bypass path; the control method for controlling opening and closing of the bypass pipe of the three-pipe type multi-split air conditioning system comprises the steps that when the three-pipe type multi-split air conditioning system operates in a pure refrigeration mode, the refrigeration load is detected; if it is detected that the refrigeration load reaches the first threshold value, a high-pressure air pipe electromagnetic valve is closed, and a main air pipe switching electromagnetic valve is opened; opening a low-pressure side switching valve and a high-pressure side switching valve which are connected with a refrigeration indoor unit in the branch box; a low-pressure air cooling medium evaporated in the indoor heat exchanger flows to the two sides of the low-pressure main air pipe and the high-pressure main air pipe, flows to the low-pressure air pipe through the main air pipe switching electromagnetic valve and is sucked by the compressor. The problem of how to prevent the refrigerating capacity of the three-pipe type multi-split air conditioner system from being reduced when the long piping is installed is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning, and in particular to a three-pipe multi-connected system and a control method thereof. Background Art

[0002] With the continuous development of science and technology, air conditioner technology is also innovating day by day. There is a three-pipe multi-split system that faces technical challenges when installed over long distances. When the outdoor unit is far away from the indoor unit (for example, 200 meters), the density of the refrigerant pressing against the main air pipe becomes smaller and the flow rate becomes faster, resulting in a significant increase in pressure drop (for example, more than 4 bar). The increase in pressure drop will cause the evaporation temperature of the indoor heat exchanger to increase, thereby reducing the evaporation capacity and overall cooling capacity (for example, a decrease of more than 50%). The traditional solution is to reduce the refrigerant flow rate and pressure drop by reducing the pipe diameter; expanding the pipe diameter will increase material and construction costs, especially when installed over long distances; after expanding the pipe diameter, the refrigerant flow rate is reduced, which may cause the compressor oil discharge to be unable to return effectively, ultimately resulting in insufficient oil in the compressor and damage to the compressor. It can be seen that solving the pressure drop problem during long-distance installation while also taking into account the stability and reliability of the system is a difficult technical problem to solve. Summary of the invention

[0003] The problem solved by the invention is how to solve the problem of preventing the refrigeration capacity of a three-pipe multi-connected system from decreasing when installing long pipes.

[0004] In order to solve the above problems, the present invention provides a three-pipe multi-split system, comprising: an outdoor unit, a branch box and an indoor unit, wherein the outdoor unit comprises: a compressor, a compressor exhaust pipe, a compressor suction pipe, a high-pressure main gas pipe connecting part and a low-pressure main gas pipe connecting part of a four-way valve; the branch box comprises a high-pressure side switching valve and a low-pressure side switching valve; the indoor unit comprises an indoor heat exchanger and an indoor expansion valve; a high-pressure main gas pipe is provided between the high-pressure main gas pipe connecting part and the high-pressure side switching valve; a low-pressure main gas pipe is provided between the low-pressure main gas pipe connecting part and the low-pressure side switching valve; Among them, a high-pressure air pipe solenoid valve is installed on the high-pressure air pipe between the compressor exhaust pipe and the high-pressure main air pipe connection part, and the high-pressure air pipe solenoid valve is used to control the opening and closing of the high-pressure air pipe; the high-pressure air pipe between the high-pressure air pipe solenoid valve and the high-pressure main air pipe connection part, to the low-pressure air pipe between the four-way valve and the low-pressure main air pipe connection part, is provided with a main air pipe switching bypass pipe, and the main air pipe switching bypass valve provides a bypass path; the main air pipe switching solenoid valve is installed in the main air pipe switching bypass pipe, and the main air pipe switching solenoid valve is used to control the opening and closing of the bypass pipe.

[0005] The technical effect achieved after adopting this technical solution is as follows: by installing a high-pressure air pipe solenoid valve on the high-pressure air pipe, the opening and closing of the high-pressure air pipe can be flexibly controlled, so that the system can adjust the working state according to actual needs; the design of the main air pipe switching bypass pipe and the main air pipe switching solenoid valve provides an additional bypass path, which can not only maintain the normal operation of the system under certain specific circumstances, but also optimize the airflow distribution under different working conditions, thereby improving the adaptability and reliability of the system.

[0006] Furthermore, a compressor suction pressure sensor for measuring the compressor suction pressure is installed on the compressor suction pipe; an indoor low-pressure air pipe pressure sensor for measuring the indoor low-pressure air pipe pressure is installed on the indoor unit side of the low-pressure main air pipe.

[0007] The technical effects achieved after adopting this technical solution are: by real-time monitoring of key pressure values ​​through sensors, the operating status of the system can be understood in a timely manner; control is performed based on actual measured data, which improves the accuracy and reliability of control.

[0008] Furthermore, the evaporation temperature is measured by an evaporation temperature sensor installed on the refrigerant pipe between the indoor expansion valve of the indoor unit and the center of the indoor heat exchanger.

[0009] The technical effects achieved after adopting this technical solution are: the low-pressure air pipe pressure is indirectly measured through the evaporation temperature, which simplifies the layout of the sensor; the saturation pressure calculated based on the evaporation temperature is controlled, which improves the accuracy of control.

[0010] In order to solve the above problems, the present invention provides a control method for a three-pipe multi-split system, which is implemented by any of the three-pipe multi-split systems described above. The three-pipe multi-split system includes an outdoor unit, a branch box and an indoor unit, wherein the outdoor unit includes: a compressor, a compressor exhaust pipe, a compressor suction pipe, a four-way valve, a high-pressure main air pipe connection part and a low-pressure main air pipe connection part; the branch box includes a high-pressure side switching valve and a low-pressure side switching valve; the indoor unit includes an indoor heat exchanger and an indoor expansion valve; a high-pressure main air pipe is provided between the high-pressure main air pipe and the high-pressure side switching valve; a high-pressure main air pipe is provided between the low-pressure main air pipe and the low-pressure side switching valve A low-pressure main air pipe is provided; the control method of the three-pipe multi-split system includes: when operating in pure refrigeration mode, detecting the refrigeration load; if it is detected that the refrigeration load reaches a first threshold, closing the high-pressure air pipe solenoid valve and opening the main air pipe switching solenoid valve; opening the low-pressure side switching valve and the high-pressure side switching valve connected to the refrigeration indoor unit in the branch box; allowing the low-pressure air refrigerant evaporated in the indoor heat exchanger to flow to both sides of the low-pressure main air pipe and the high-pressure main air pipe, and flow to the low-pressure air pipe through the main air pipe switching solenoid valve; allowing the low-pressure air refrigerant flowing through the low-pressure main air pipe and the high-pressure main air pipe to merge in the low-pressure pipe and be sucked into the compressor.

[0011] The technical effects achieved after adopting this technical solution are as follows: through the cooperation of the high-pressure gas pipe solenoid valve and the main gas pipe solenoid valve, the refrigerant flow path can be adjusted according to the actual operating conditions, thereby optimizing the system performance; when the refrigeration load is large, the bypass path can effectively reduce the pressure drop of the low-pressure main gas pipe and improve the refrigeration efficiency; the installed control valve provides additional control means and enhances the flexibility and adaptability of the system; by reducing the pressure drop of the low-pressure main gas pipe, the evaporation temperature in the indoor heat exchanger can be prevented from rising, thereby maintaining a high refrigeration capacity; ensuring the system stability and reliability under high load.

[0012] Furthermore, the control method of the three-pipe multi-split system also includes: if it is detected that the refrigeration load has not reached the first threshold, the high-pressure gas pipe solenoid valve is opened and the main gas pipe switching solenoid valve is closed; the low-pressure side switching valve connected to the refrigeration indoor unit in the branch box is opened, and the high-pressure side switching valve is closed; the low-pressure gas refrigerant evaporated in the indoor heat exchanger of the refrigeration indoor unit only flows to the low-pressure main gas pipe.

[0013] The technical effects achieved after adopting this technical solution are as follows: Under low refrigeration load, maintaining the traditional flow path can prevent oil retention problems caused by slow flow rate; ensure the lubrication of the compressor and avoid mechanical wear caused by insufficient oil; under low load, the system can operate with lower energy consumption and improve energy efficiency.

[0014] Furthermore, a compressor suction pressure sensor is installed on the compressor suction pipe to measure the compressor suction pressure; an indoor low-pressure air pipe pressure sensor is installed at the indoor unit measuring position lower than the main air pipe to measure the indoor low-pressure air pipe pressure.

[0015] The technical effects achieved after adopting this technical solution are: by real-time monitoring of key pressure values ​​through sensors, the operating status of the system can be understood in a timely manner; control is performed based on actual measured data, which improves the accuracy and reliability of control; real-time monitoring helps to detect potential faults early and improve the reliability and maintenance efficiency of the system.

[0016] Furthermore, the control method of the three-pipe multi-split system includes the following steps: calculating the low-pressure gas pipe pressure drop; if the low-pressure gas pipe pressure drop reaches a preset threshold, closing the high-pressure gas pipe solenoid valve, opening the main gas pipe switching solenoid valve, and opening the low-pressure side switching valve and the high-pressure side switching valve connected to the cold indoor unit in the branch box; if the low-pressure gas pipe pressure drop does not reach the preset threshold, opening the high-pressure gas pipe solenoid valve, closing the main gas pipe switching solenoid valve, and opening the low-pressure side switching valve connected to the refrigeration indoor unit in the branch box, and closing the high-pressure side switching valve.

[0017] The technical effects achieved after adopting this technical solution are: by timely adjusting the flow path, the pressure drop of the low-pressure gas pipe is effectively reduced, thereby improving the refrigeration efficiency; ensuring that the system can still operate efficiently under high load and improving the overall performance; reducing the pressure drop helps to maintain a low evaporation temperature and maintain a good refrigeration effect.

[0018] Furthermore, an evaporation temperature sensor is installed on the refrigerant pipe between the indoor expansion valve of the indoor unit and the central part of the indoor heat exchanger to measure the evaporation temperature.

[0019] The technical effects achieved after adopting this technical solution are: the low-pressure gas pipe pressure is indirectly measured through the evaporation temperature, which simplifies the sensor layout; the saturation pressure calculated based on the evaporation temperature is controlled, which improves the accuracy of control.

[0020] Furthermore, the control method of the three-pipe multi-split system includes the following steps: using the saturated pressure formula of the refrigerant to calculate the evaporation pressure, and regarding the evaporation pressure as the low-pressure gas pipe pressure on the indoor side; calculating the low-pressure pipe pressure drop; if the low-pressure gas pipe pressure drop reaches a preset threshold, closing the high-pressure gas pipe solenoid valve, opening the main gas pipe switching valve, and opening the low-pressure side switching valve and the high-pressure switching valve connected to the refrigeration indoor unit in the branch box.

[0021] The technical effects achieved after adopting this technical solution are: ensuring the normal operation of the system under high load and improving system efficiency; ensuring that the system can still operate efficiently under high load and improving overall performance.

[0022] Furthermore, if the pressure drop of the low-pressure gas pipe does not reach the preset threshold, the high-pressure gas pipe solenoid valve is opened, the main gas pipe switching solenoid valve is closed, and the low-pressure side switching valve of the branch box connected to the refrigeration indoor unit is opened, and the high-pressure side switching valve is closed.

[0023] The technical effect achieved after adopting this technical solution is: ensuring the normal operation of the system under low load and improving system efficiency; under low load, the system can operate with lower energy consumption and improve energy efficiency.

[0024] In summary, the above-mentioned technical solutions of the present application may have one or more of the following advantages or beneficial effects: i) The control valve accurately controls each pipeline, competing for system flexibility. ii) With the help of various sensors in the system, the control accuracy is optimized. iii) By accurately controlling the working state of the compressor, the service life of the components in the system is extended. iv) This design allows fault repair diagnosis and maintenance of individual components without stopping the entire system, which not only reduces downtime but also reduces maintenance costs. v) By accurately calculating the refrigeration load, more effective control can be performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1This is a schematic diagram of a first structure of a three-tube multi-connected system in an embodiment of the present invention; Figure 2 This is a first flow chart of a three-tube multi-connected system control method in an embodiment of the present invention; Figure 3 A second structural schematic diagram of a three-tube multi-connected system in an embodiment of the present invention; Figure 4 This is a second flow chart of the three-tube multi-connected system control method in an embodiment of the present invention; Figure 5 A third structural schematic diagram of a three-tube multi-connected system in an embodiment of the present invention; Figure 6 This is a third flow chart of the three-tube multi-connected system control method in an embodiment of the present invention.

[0026] Description of reference numerals: 100-three-pipe multi-split system; 110-outdoor unit; 111-high-pressure gas pipe solenoid valve; 112-four-way valve; 113-main gas pipe switching solenoid valve; 114-main gas pipe switching bypass pipe; 115-compressor exhaust pipe; 116-compressor suction pipe; 117-compressor; 118-high-pressure main gas pipe connection; 119-low-pressure main gas pipe connection; 120-manifold box; 121-low-pressure side switching valve; 122-high-pressure side switching valve; 130-indoor unit; 131-indoor heat exchanger; 132-indoor expansion valve; 140-high-pressure main gas pipe; 150-low-pressure main gas pipe; 160-compressor suction pressure sensor; 170-indoor low-pressure gas pipe pressure sensor; 180-evaporation temperature sensor; 190-main liquid pipe. DETAILED DESCRIPTION

[0027] The object of the present invention is to provide a three-pipe multi-split system and a control method for achieving the effect of preventing the refrigeration capacity of the three-pipe multi-split system from decreasing when installing long pipes.

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0029] See also Figure 1The present invention provides a three-pipe multi-split system 100, comprising: an outdoor unit 110, a branch box 120 and an indoor unit 130, wherein the outdoor unit 110 comprises: a compressor 117, a compressor exhaust pipe 115, a compressor suction pipe 116, a four-way valve 112, a high-pressure main gas pipe connection 118 and a low-pressure main gas pipe connection part 119; the branch box 120 comprises a high-pressure side switching valve 122 and a low-pressure side switching valve 121; the indoor unit 130 comprises an indoor heat exchanger 131 and an indoor expansion valve 132; a high-pressure main gas pipe 140 is provided between the high-pressure main gas pipe connection part 118 and the high-pressure side switching valve 122; a low-pressure main gas pipe 150 is provided between the low-pressure main gas pipe connection part 119 and the low-pressure side switching valve 121 ; Among them, a high-pressure gas pipe solenoid valve 111 is installed on the high-pressure gas pipe between the compressor exhaust pipe 115 and the high-pressure main gas pipe connection part 118, and the high-pressure gas pipe solenoid valve 111 is used to control the opening and closing of the high-pressure gas pipe; the high-pressure gas pipe between the high-pressure gas pipe solenoid valve 111 and the high-pressure main gas pipe connection part 118, to the low-pressure gas pipe between the four-way valve 112 and the low-pressure main gas pipe connection part 119, is provided with a main gas pipe switching bypass pipe 114, and the main gas pipe switching bypass valve provides a bypass path; the main gas pipe switching bypass pipe 114 is installed with a main gas pipe switching solenoid valve 113, and the main gas pipe switching solenoid valve 113 is used to control the opening and closing of the bypass pipe; the four-way valve 112 is connected to the indoor unit 130 through the main liquid pipe 190.

[0030] In this embodiment, by installing a high-pressure air pipe solenoid valve 111 on the high-pressure air pipe, the opening and closing of the high-pressure air pipe can be flexibly controlled, so that the system can adjust the working state according to actual needs; the design of the main air pipe switching bypass pipe 114 and the main air pipe switching solenoid valve 113 provides an additional bypass path, which can not only maintain the normal operation of the system under certain specific circumstances, but also optimize the airflow distribution under different working conditions, thereby improving the adaptability and reliability of the system.

[0031] Specifically, this is a structural diagram of the first method. In the three-pipe multi-connected system of the first invention, a high-pressure gas pipe solenoid valve 111 is installed on the high-pressure gas pipe between the compressor exhaust pipe 115 and the high-pressure main gas pipe connection part 118; a main gas pipe switching bypass pipe 114 is installed, ranging from the high-pressure gas pipe between the high-pressure gas pipe solenoid valve 111 and the high-pressure main gas pipe connection part 118 to the low-pressure gas pipe between the four-way valve 112 and the low-pressure main gas pipe connection part 119. Then, a main gas pipe switching solenoid valve 113 is installed in the main gas pipe switching bypass pipe 114.

[0032] See also Figure 3 A compressor suction pressure sensor 160 for measuring the compressor suction pressure is installed on the compressor suction pipe 116; an indoor low-pressure air pipe pressure sensor 170 for measuring the indoor low-pressure air pipe pressure is installed on the side of the indoor unit 130 of the low-pressure main air pipe.

[0033] In this embodiment, by monitoring the key pressure values ​​in real time through sensors, the operating status of the system can be understood in a timely manner; control is performed based on actual measured data, thereby improving the accuracy and reliability of control.

[0034] Specifically, the compressor 117 suction pressure sensor 160 is installed on the compressor suction pipe 116; the indoor low-pressure air pipe pressure sensor 170 is installed between the low-pressure main air pipe and the low-pressure side switching valve 121; the pressure value is monitored in real time, the system operation status is understood in real time, and the refrigerant circulation is controlled in time.

[0035] See also Figure 5 The evaporation temperature is measured by an evaporation temperature sensor 180 installed on the refrigerant pipe between the indoor expansion valve 132 of the indoor unit 130 and the central part of the indoor heat exchanger 131.

[0036] In this embodiment, the low-pressure gas pipe pressure is indirectly measured by the evaporation temperature, which simplifies the layout of the sensor; the saturation pressure calculated based on the evaporation temperature is controlled, which improves the accuracy of the control.

[0037] Specifically, the evaporating temperature sensor 180 is installed on the refrigerant pipe between the indoor expansion valve 132 of the indoor unit 130 and the central part of the indoor heat exchanger 131 to monitor the temperature in real time and perform macro-control on the refrigerant circulation.

[0038] See also Figure 1 and Figure 2The present invention provides a control method for a three-pipe multi-split system 100, which is implemented by any of the three-pipe multi-split systems described above. The three-pipe multi-split system 100 includes an outdoor unit 110, a branch box 120 and an indoor unit 130, wherein the outdoor unit 110 includes: a compressor 117, a compressor exhaust pipe 115, a compressor suction pipe 116, a four-way valve 112, a high-pressure main gas pipe connection part 118 and a low-pressure main gas pipe connection part 119; the branch box 120 includes a high-pressure side switching valve 122 and a low-pressure side switching valve 121; the indoor unit 130 includes an indoor heat exchanger 131 and an indoor expansion valve 132; a high-pressure main gas pipe 140 is provided between the high-pressure main gas pipe and the high-pressure side switching valve 122; and a low-pressure main gas pipe and a low-pressure side switching valve are connected. A low-pressure main air pipe 150 is provided between 121; the control method of the three-pipe multi-split system 100 includes: when operating in pure refrigeration mode, detecting the refrigeration load; if it is detected that the refrigeration load reaches a first threshold, closing the high-pressure air pipe solenoid valve 111 and opening the main air pipe switching solenoid valve 113; opening the low-pressure side switching valve 121 and the high-pressure side switching valve 122 connected to the refrigeration indoor unit 130 in the branch box 120; allowing the low-pressure gas refrigerant evaporated in the indoor heat exchanger 131 to flow to both sides of the low-pressure main air pipe 150 and the high-pressure main air pipe 140, and flow to the low-pressure air pipe through the main air pipe switching solenoid valve 113; allowing the low-pressure gas refrigerant flowing through the low-pressure main air pipe 150 and the high-pressure main air pipe 140 to merge in the low-pressure pipe and be sucked into the compressor 117.

[0039] In this embodiment, through the cooperation of the high-pressure air pipe solenoid valve 111 and the main air pipe solenoid valve, the refrigerant flow path can be adjusted according to the actual operating conditions, thereby optimizing the system performance; when the refrigeration load is large, the bypass path can effectively reduce the pressure drop of the low-pressure main air pipe 150 and improve the refrigeration efficiency; the installed control valve provides additional control means and enhances the flexibility and adaptability of the system; by reducing the pressure drop of the low-pressure main air pipe 150, the evaporation temperature in the indoor heat exchanger 131 can be prevented from rising, thereby maintaining a high refrigeration capacity; ensuring the system stability and reliability under high load.

[0040] Specifically, see Figure 1 and Figure 2 This is the first method. When performing pure refrigeration operation, the refrigeration load is detected. If the load is large, the high-pressure gas pipe solenoid valve 111 is closed and the main gas pipe switching solenoid valve 113 is opened. At the same time, the low-pressure side switching valve 121 and the high-pressure side switching valve 122 connected to the refrigeration indoor unit 130 in the branch box are opened. Next, the ratio of the refrigeration load to the operating capacity of the refrigeration indoor unit 130 is used for determination. The following [Formula 1] is a formula for calculating the pressure drop.

[0041]

Formula 1

[0042] Preferably, see Figure 3 , the low-pressure gas refrigerant evaporated in the indoor heat exchanger 131 of the refrigeration indoor unit 130 flows to both sides of the low-pressure main air pipe 150 and the high-pressure main air pipe 140, and flows to the outdoor unit 110. Among them, since the high-pressure air pipe solenoid valve 111 is closed, the low-pressure gas refrigerant flowing through the high-pressure main air pipe 140 flows to the low-pressure air pipe through the main air pipe switching solenoid valve 113. Here, it merges with the low-pressure gas refrigerant flowing through the low-pressure main air pipe 150 and is sucked into the compressor 117. As a result, compared with the case where the low-pressure gas refrigerant only flows through the low-pressure main air pipe 150, the refrigerant flow rate slows down. This can reduce the pressure drop in the low-pressure main air pipe 150. For example, when the inner diameter of the low-pressure main air pipe 150 is φ26.6mm and the inner diameter of the high-pressure main air pipe 140 is φ17.1mm, the refrigerant flow rate of the low-pressure main air pipe 150 can be slowed down by 19%. Finally, the pressure drop is reduced by 42%. Therefore, when the outdoor unit 110 is installed far from the indoor unit 130, the pressure drop caused by the high refrigerant flow rate of the low-pressure main air pipe 150 can be prevented from increasing, thereby preventing the refrigeration capacity from decreasing due to the increase in the evaporation temperature in the indoor heat exchanger 131.

[0043] See also Figure 1 and Figure 2 The control method of the three-pipe multi-split system also includes: if it is detected that the refrigeration load has not reached the first threshold, the high-pressure gas pipe solenoid valve 111 is opened and the main gas pipe switching solenoid valve 113 is closed; the low-pressure side switching valve 121 connected to the refrigeration indoor unit 130 in the branch box 120 is opened, and the high-pressure side switching valve 122 is closed; the low-pressure gas refrigerant evaporated in the indoor heat exchanger 131 of the refrigeration indoor unit 130 only flows to the low-pressure main gas pipe 150.

[0044] In this embodiment, under low refrigeration load, maintaining the traditional flow path can prevent oil retention problems caused by too slow flow rate; ensure the lubrication of the compressor 117 and avoid mechanical wear caused by insufficient oil; under low load, the system can operate with lower energy consumption and improve energy efficiency.

[0045] Preferably, see Figure 4 When the refrigeration load is detected to be small, the high-pressure gas pipe solenoid valve 111 is opened and the main gas pipe switching solenoid valve 113 is closed. At the same time, the low-pressure side switching valve 121 connected to the refrigeration indoor unit 130 in the branch box is opened, and the high-pressure side switching valve 122 is closed. After the above actions are performed, Figure 4 As shown, the low-pressure gas refrigerant evaporated in the indoor heat exchanger 131 of the refrigeration indoor unit 130 only flows to the low-pressure main air pipe 150, and the refrigerant flow rate of the main air pipe will not slow down. Therefore, oil retention and insufficient oil in the compressor 117 caused by the slowing down of the refrigerant flow rate of the low-pressure main air pipe 150 can be prevented.

[0046] See also Figure 3 and Figure 4 A compressor suction pressure sensor 160 is installed on the compressor 117 suction pipe 116 to measure the compressor suction pressure; an indoor low-pressure air pipe pressure sensor 170 is installed at a position of the indoor unit 130 below the main air pipe to measure the indoor low-pressure air pipe pressure.

[0047] In this embodiment, by real-time monitoring of key pressure values ​​through sensors, the operating status of the system can be understood in a timely manner; control based on actual measured data improves the accuracy and reliability of control; real-time monitoring helps to discover potential faults early and improve the reliability and maintenance efficiency of the system.

[0048] Specifically, see Figure 3 and Figure 4 This is the second method. Install a pressure gauge to measure the compressor suction pressure on the compressor suction pipe 116. The compressor suction pressure sensor 160 is installed at the indoor unit 130 side of the low-pressure main air pipe 150 to measure the indoor low-pressure air pipe pressure. The indoor low-pressure gas pipe pressure sensor 170. The indoor low-pressure gas pipe pressure sensor 170 can be installed inside the branch box or outside. When performing pure cooling operation, the low-pressure gas pipe pressure drop △ is calculated by the compressor suction pressure and the indoor low-pressure gas pipe pressure according to the following [Formula 2]. .

[0049]

Formula 2

[0050] In this embodiment, by timely adjusting the flow path, the pressure drop of the low-pressure gas pipe is effectively reduced, thereby improving the refrigeration efficiency; ensuring that the system can still operate efficiently under high load and improving the overall performance; reducing the pressure drop helps to maintain a low evaporation temperature and maintain a good refrigeration effect.

[0051] Specifically, when the calculated △ When the pressure reaches a certain value, for example, 1 bar or more, the high-pressure gas pipe solenoid valve 111 is closed and the main gas pipe switching solenoid valve 113 is opened. At the same time, the low-pressure side switching valve 121 and the high-pressure side switching valve 122 connected to the refrigeration indoor unit 130 in the branch box are also opened. Through the above actions, the same effect as when the refrigeration load is large in the first invention mode can be achieved, that is, the refrigeration capacity reduction caused by the increase in the evaporation temperature in the indoor heat exchanger 131 is prevented.

[0052] When the calculated △ When the pressure does not reach a certain value, for example, less than 1 bar, the high-pressure gas pipe solenoid valve 111 is opened and the main gas pipe switching solenoid valve 113 is closed. At the same time, the low-pressure side switching valve 121 connected to the refrigeration indoor unit 130 in the branch box is opened, and the high-pressure side switching valve 122 is closed. Through the above actions, the same effect as the first invention mode of the refrigeration load is small, that is, oil retention caused by the slow flow rate of the refrigerant in the low-pressure main gas pipe 150 and insufficient oil in the compressor 117 can be prevented.

[0053] In addition, since the increase in the pressure drop of the low-pressure gas pipe is not calculated by the refrigeration load or the number of revolutions of the compressor 117, but is calculated by the measured value of the pressure, the accuracy of the determination of the increase in the pressure drop of the low-pressure gas pipe can be improved. This ensures that insufficient refrigeration capacity caused by a large pressure drop in the low-pressure gas pipe or insufficient oil in the compressor 117 caused by a slow flow rate of the refrigerant in the low-pressure main gas pipe 150 can be prevented.

[0054] See also Figure 1 and Figure 2 An evaporation temperature sensor 180 is installed on the refrigerant pipe between the indoor expansion valve 132 of the indoor unit 130 and the central part of the indoor heat exchanger 131 to measure the evaporation temperature.

[0055] In this embodiment, the low-pressure gas pipe pressure is indirectly measured by the evaporation temperature, which simplifies the sensor layout; the saturation pressure calculated based on the evaporation temperature is controlled, which improves the accuracy of the control.

[0056] Specifically, see Figure 5 and Figure 6 This is the third method. Calculate the evaporation pressure and regard this pressure as the pressure of the indoor low-pressure gas pipe. This value-taking method is used because the indoor heat exchanger 131 that performs evaporation is close to the indoor low-pressure gas pipe, and the pressure drop is so small that it can be almost ignored. The evaporation pressure measures the evaporation temperature, and the saturation pressure of the evaporation temperature is used as the evaporation pressure. For example, the saturation pressure of the refrigerant R410A is calculated by the refrigerant temperature using the general approximation shown in the following [Formula 3]. In addition, the evaporation temperature is measured by the evaporation temperature sensor 180 installed on the refrigerant piping between the indoor expansion valve 132 of the indoor unit 130 and the central part of the indoor heat exchanger 131.

[0057]

Formula 3

[0058] See also Figure 5 and Figure 6 The control method of the three-pipe multi-split system includes the following steps: using the saturated pressure formula of the refrigerant to calculate the evaporation pressure, and regarding the evaporation pressure as the indoor low-pressure gas pipe pressure; calculating the low-pressure pipe pressure drop; if the low-pressure gas pipe pressure drop reaches a preset threshold, closing the high-pressure gas pipe solenoid valve 111, opening the main gas pipe switching valve, and opening the low-pressure side switching valve 121 and the high-pressure switching valve connected to the refrigeration indoor unit 130 in the branch box 120; In this embodiment, the system is ensured to operate normally under high load or low load, thereby improving system efficiency; the system is ensured to operate efficiently under high load, thereby improving overall performance; under low load, the system can operate with lower energy consumption, thereby improving energy efficiency.

[0059] Specifically, in the third embodiment of the invention, the evaporation pressure is obtained and regarded as the indoor low-pressure gas pipe pressure. This is because the indoor heat exchanger 131 that performs the evaporation action is close to the indoor low-pressure air pipe, and the pressure drop is so small that it can be ignored. The evaporation pressure is measured by measuring the evaporation temperature. The saturation pressure is regarded as the evaporation pressure. The saturation pressure is calculated using a general approximation similar to [Formula 4]. The temperature is measured by an evaporation temperature sensor 180 installed on the refrigerant pipe between the indoor expansion valve 132 of the indoor unit 130 and the center of the indoor heat exchanger 131 .

[0060] See also Figure 5 and Figure 6 If the pressure drop of the low-pressure gas pipe does not reach the preset threshold, the high-pressure gas pipe solenoid valve 111 is opened, the main gas pipe switching solenoid valve 113 is closed, and the low-pressure side switching valve 121 connecting the branch box 120 to the refrigeration indoor unit 130 is opened, and the high-pressure side switching valve 122 is closed.

[0061] In this embodiment, the normal operation of the system under low load is ensured to improve the system efficiency; under low load, the system can operate with lower energy consumption to improve energy efficiency.

[0062] When the present invention is used for pure refrigeration operation, the operating capacity ratio of the refrigeration indoor unit 130 to the outdoor unit capacity is detected. [%], as shown in [Formula 4].

[0063]

Formula 4

[0064] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A three-tube multi-connection system, characterized in that: include: An outdoor unit, a branch box and an indoor unit, wherein the outdoor unit includes: a compressor, a compressor exhaust pipe, a compressor suction pipe, a four-way valve, a high-pressure main gas pipe connection part and a low-pressure main gas pipe connection part; the branch box includes a high-pressure side switching valve and a low-pressure side switching valve; the indoor unit includes an indoor heat exchanger and an indoor expansion valve; a high-pressure main gas pipe is provided between the high-pressure main gas pipe connection part and the high-pressure side switching valve; a low-pressure main gas pipe is provided between the low-pressure main gas pipe connection part and the low-pressure side switching valve; Among them, a high-pressure air pipe solenoid valve is installed on the high-pressure air pipe between the compressor exhaust pipe and the high-pressure main air pipe connection part, and the high-pressure air pipe solenoid valve is used to control the opening and closing of the high-pressure air pipe; the high-pressure air pipe between the high-pressure air pipe solenoid valve and the high-pressure main air pipe connection part, to the low-pressure air pipe between the four-way valve and the low-pressure main air pipe connection part, is provided with a main air pipe switching bypass pipe, and the main air pipe switching bypass valve provides a bypass path; the main air pipe switching solenoid valve is installed in the main air pipe switching bypass pipe, and the main air pipe switching solenoid valve is used to control the opening and closing of the bypass pipe.

2. The three-pipe multi-connection system according to claim 1, characterized in that: A compressor suction pressure sensor for measuring the compressor suction pressure is installed on the compressor suction pipe; an indoor low-pressure air pipe pressure sensor for measuring the indoor low-pressure air pipe pressure is installed on the indoor unit side of the low-pressure main air pipe.

3. The three-pipe multi-connection system according to claim 2, characterized in that: The evaporating temperature is measured by an evaporating temperature sensor installed on a refrigerant pipe between the indoor expansion valve and the center portion of the indoor heat exchanger of the indoor unit.

4. A control method for a three-pipe multi-connected system, characterized in that: The method is implemented by the three-pipe multi-split system according to any one of claims 1 to 3, wherein the three-pipe multi-split system comprises an outdoor unit, a branch box and an indoor unit, wherein the outdoor unit comprises: a compressor, a compressor exhaust pipe, a compressor suction pipe, a high-pressure main air pipe connecting part and a low-pressure main air pipe connecting part of a four-way valve; the branch box comprises a high-pressure side switching valve and a low-pressure side switching valve; the indoor unit comprises an indoor heat exchanger and an indoor expansion valve; a high-pressure main air pipe is provided between the high-pressure main air pipe and the high-pressure side switching valve; a low-pressure main air pipe is provided between the low-pressure main air pipe and the low-pressure side switching valve; The control method of the three-pipe multi-connected system includes: When operating in pure cooling mode, detect the cooling load; If it is detected that the refrigeration load reaches the first threshold, the high-pressure gas pipe solenoid valve is closed and the main gas pipe switching solenoid valve is opened; Open the low-pressure switching valve and high-pressure switching valve connected to the refrigeration indoor unit in the branch box; The low-pressure gas refrigerant evaporated in the indoor heat exchanger flows to both sides of the low-pressure main gas pipe and the high-pressure main gas pipe, and flows to the low-pressure gas pipe through the main gas pipe switching solenoid valve; The low-pressure refrigerant flowing through the low-pressure main air pipe and the high-pressure main air pipe merges in the low-pressure pipe and is sucked into the compressor.

5. The control method of the three-pipe multi-connected system according to claim 4, characterized in that: Also includes: If it is detected that the refrigeration load does not reach the first threshold, the high-pressure gas pipe solenoid valve is opened and the main gas pipe switching solenoid valve is closed; Open the low-pressure switching valve connected to the refrigeration indoor unit in the branch box, and close the high-pressure switching valve; The low-pressure gas refrigerant evaporated in the indoor heat exchanger of the refrigeration indoor unit only flows to the low-pressure main air pipe.

6. The control method of the three-pipe multi-connected system according to claim 4, characterized in that: The compressor suction pressure sensor is installed on the compressor suction pipe to measure the compressor suction pressure; The indoor low-pressure air pipe pressure sensor is installed at the indoor unit measuring position lower than the main air pipe to measure the indoor low-pressure air pipe pressure.

7. The control method of the three-pipe multi-connected system according to claim 6, characterized in that: The following steps are involved: Calculate the pressure drop in the low pressure gas pipe; If the pressure drop of the low-pressure gas pipe reaches the preset threshold, the high-pressure gas pipe solenoid valve is closed, the main gas pipe switching solenoid valve is opened, and the low-pressure side switching valve and the high-pressure side switching valve connected to the cold indoor unit in the branch box are opened; If the pressure drop of the low-pressure gas pipe does not reach the preset threshold, the high-pressure gas pipe solenoid valve is opened, the main gas pipe switching solenoid valve is closed, and the low-pressure side switching valve connected to the refrigeration indoor unit in the branch box is opened, and the high-pressure side switching valve is closed.

8. The control method of the three-pipe multi-connected system according to claim 6, characterized in that: The evaporation temperature sensor is installed on the refrigerant pipe between the indoor expansion valve of the indoor unit and the central part of the indoor heat exchanger to measure the evaporation temperature.

9. The control method of the three-pipe multi-connected system according to claim 8, characterized in that: The following steps are involved: Use the refrigerant saturation pressure formula to calculate the evaporation pressure, and regard the evaporation pressure as the low-pressure gas pipe pressure on the indoor side; Calculate the pressure drop of the low-pressure pipe; If the pressure drop of the low-pressure gas pipe reaches the preset threshold, the high-pressure gas pipe solenoid valve is closed, the main gas pipe switching valve is opened, and the low-pressure side switching valve and the high-pressure switching valve connected to the refrigeration indoor unit in the branch box are opened.

10. According to the control method of the three-pipe multi-split system as described in claim 8, if the pressure drop of the low-pressure gas pipe does not reach the preset threshold, the high-pressure gas pipe solenoid valve is opened, the main gas pipe switching solenoid valve is closed, and the low-pressure side switching valve of the branch box connected to the refrigeration indoor unit is opened, and the high-pressure side switching valve is closed.

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