Multifunctional oil return system of refrigerating unit and control method of multifunctional oil return system

Abstract

The invention discloses a multifunctional oil return system of a refrigerating unit and a control method of the multifunctional oil return system. The system comprises a control unit, a refrigerant circulation loop and an oil return control assembly integrated in the refrigerant circulation loop. The refrigerant circulation loop is sequentially connected with a compressor, an oil separator, a condenser, a throttling device and an evaporator; the oil return control assembly comprises an execution assembly, a monitoring assembly and a connecting pipeline. The system integrates multiple functions, all-working-condition efficient oil return is achieved through the liquid taking pump and the load judgment module, dynamic balance of oil return is achieved by integrating multiple monitoring assemblies and the control unit, and by means of integrated heating, filtering and other functions of the oil return tank and linkage control logic, the oil return efficiency is improved. And full-working-condition automatic adjustment, abnormal condition quick response and ordered control in the shutdown and starting stage are achieved, various problems existing in a traditional mode are effectively solved, and the operation efficiency and safety of the unit are comprehensively improved.

Description

Technical Field

[0001] This invention belongs to the field of refrigeration machinery control and regulation technology, and particularly relates to a multi-functional oil return system for refrigeration units and its control method. Background Technology

[0002] In refrigeration units using oil-lubricated compressors, some lubricating oil accumulates in the evaporator, reducing its heat exchange efficiency and potentially jeopardizing operational safety due to insufficient oil in the compressor. Therefore, it is necessary to effectively recover the lubricating oil from the evaporator. Currently, the mainstream ejector pump oil return method has significant drawbacks: First, it relies on the compressor's suction and discharge pressure difference, and the oil return efficiency drops sharply under low load and low pressure difference conditions; second, the liquid volume needs to be manually adjusted, which can easily lead to poor oil return or excessive liquid refrigerant entering the compressor; third, when a large amount of lubricating oil accumulates in the evaporator and the compressor's oil chamber is short of oil, there is a lack of convenient rescue measures, and additional oil must be added. Furthermore, existing oil return methods are limited in function and cannot coordinate and control flow rate, temperature, liquid level, and pressure during the oil return process. This makes it difficult to meet the oil return requirements of the unit under all operating conditions, and it also cannot monitor and intelligently adjust the system status in real time, thus restricting the reliability of oil return and the safety of unit operation. In view of the above reasons, this application proposes a multi-functional oil return system for refrigeration units and its control method. Summary of the Invention

[0003] Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a multi-functional oil return system for refrigeration units and its control method.

[0004] Technical solution To achieve the above objectives, the present invention provides the following technical solution: a control system for a direct expansion evaporator. The system includes a control unit, a refrigerant circulation loop, and an oil return control component integrated into the refrigerant circulation loop. The refrigerant circulation loop is sequentially connected to a compressor, an oil separator, a condenser, a throttling device, and an evaporator. The oil return control component includes an execution component, a monitoring component, and connecting pipelines. The execution component includes a liquid sampling filter, a liquid sampling pump, a liquid sampling solenoid valve, a check valve, an oil return tank, an oil separator solenoid valve, an oil supply filter, an oil supply solenoid valve, a proportional regulating valve, and an oil heater. The monitoring component includes an oil flow switch, an oil temperature sensor, a liquid level sensor, and a pressure sensor. The control unit is electrically connected to the execution component and the monitoring component, receives signals from the monitoring component, and controls the action of the execution component to realize multi-functional oil return control of the refrigeration unit.

[0005] Preferably, the return oil tank is connected to the evaporator, oil separator, and compressor via pipelines; The oil inlet of the return tank is connected to the one-way valve, the liquid extraction solenoid valve, the liquid extraction pump, and the liquid extraction filter in sequence through pipelines, and then connected to the liquid extraction port of the evaporator. The oil inlet of the return oil tank is connected to the oil separator solenoid valve via a pipeline, and then connected to the oil outlet of the oil separator. The oil supply end of the return oil tank is connected to the oil supply filter, oil supply solenoid valve, and oil flow switch in sequence through pipelines, and then connected to the oil inlet end of the compressor. The exhaust port of the oil return tank is connected to the air inlet of the evaporator via a pipeline connected to a proportional regulating valve.

[0006] Preferably, the control unit is electrically connected to the oil flow switch and receives the lubricating oil flow signal fed back by the oil flow switch; When the flow rate is lower than the set threshold, the control unit increases the opening of the proportional regulating valve and increases the operating frequency of the liquid pump until the flow rate reaches the preset threshold. The control unit is electrically connected to the oil temperature sensor, which is installed on the pipeline between the oil flow switch and the compressor to receive the lubricating oil temperature signal. If the temperature is lower than the set value, the control unit will activate the oil heater built into the return oil tank and close the oil supply solenoid valve. If the temperature reaches the set value, the control unit shuts off the oil heater and opens the oil supply solenoid valve.

[0007] Preferably, the level sensor and pressure sensor are installed on the return oil tank, and the control unit is electrically connected to the level sensor to receive the oil level signal in the return oil tank; If the oil level is higher than the upper limit threshold, the control unit closes the liquid intake solenoid valve and the oil separator solenoid valve. If the oil level is below the lower threshold, the control unit simultaneously opens the liquid extraction solenoid valve and the oil separator solenoid valve, and increases the operating power of the liquid extraction pump.

[0008] Preferably, the control unit is electrically connected to the pressure sensor to receive the pressure signal from the return oil tank; If the pressure exceeds the safety threshold, the control unit increases the opening of the proportional control valve; If the pressure is lower than the minimum working pressure, the control unit reduces the opening of the proportional regulating valve and reduces the operating frequency of the liquid extraction pump.

[0009] Preferably, the control unit is linked and controlled with the liquid dispensing pump and the liquid dispensing solenoid valve; During the unit startup process, the control unit opens the liquid extraction solenoid valve. After the liquid extraction solenoid valve opens for - seconds, the control unit starts the liquid extraction pump. The refrigerant filtered by the liquid extraction filter carries the lubricating oil into the oil return tank through the one-way valve. When the unit performs a shutdown operation, the control unit issues a command to shut down the liquid extraction pump. After the liquid extraction pump shuts down for - seconds, the control unit closes the liquid extraction solenoid valve.

[0010] Preferably, the control unit is linked to the oil separator solenoid valve and the oil supply solenoid valve for control. When the oil supply solenoid valve is open, the control unit adjusts the opening degree of the oil separator solenoid valve according to the oil level signal; When the oil supply solenoid valve is closed, the control unit simultaneously closes the oil separator solenoid valve.

[0011] Preferably, the control unit includes a load determination module; The load judgment module detects that the compressor is under low load, and the control unit increases the output pressure of the liquid pump and increases the opening of the proportional regulating valve to maintain the effective power of the oil return system. The compressor resumes its rated load, and the control unit automatically reverts to normal control parameters.

[0012] Preferably, the return oil tank includes a tank body, an oil supply port, an oil inlet, and a liquid inlet. The one-way valve is located on the connecting pipeline between the liquid-taking solenoid valve and the liquid inlet. The oil supply port is located below the oil inlet. The top of the tank body is equipped with a liquid level sensor that runs through the entire tank body from top to bottom. The tank body is equipped with a filter screen, an upper baffle, and a lower baffle in sequence from top to bottom. The liquid inlet and the oil inlet are positioned at a height higher than the upper baffle. Both the lower baffle and the upper baffle have baffle notches. The oil heater is located at the bottom of the tank body, below the liquid inlet. The oil separator solenoid valve is located between the oil inlet and the oil separator. The oil supply filter, the oil supply solenoid valve, and the oil flow switch are connected in sequence. The oil temperature sensor is installed on the pipeline between the oil flow switch and the compressor. The proportional regulating valve is connected to the air inlet of the evaporator.

[0013] This invention also proposes a control method for a multi-functional oil return system of a refrigeration unit, the method comprising the following steps: Step 1: System Initialization: The control unit starts and detects the initial signals from the oil flow switch, oil temperature sensor, liquid level sensor, and pressure sensor, and shuts down all actuators. Step 2, Unit Start-up: The control unit first opens the liquid extraction solenoid valve, and after a delay of - seconds, starts the liquid extraction pump. Once it is running stably, the oil separator solenoid valve and the oil supply solenoid valve are opened according to the initial oil level in the return oil tank. Step 3, Flow Regulation: The control unit receives the oil flow switch signal to adjust the flow rate; Step 4, Oil Temperature Adjustment: The control unit receives temperature data collected by the oil temperature sensor, compares it with the temperature setpoint, and controls the opening and closing of the oil heater and the oil supply solenoid. Step 5, Oil Level Adjustment: The control unit adjusts the power of the liquid intake solenoid valve and the oil separator solenoid valve based on the oil level data monitored by the liquid level sensor. Step 6, Pressure Regulation: The control unit is used to receive pressure sensor signals and adjust the opening of the proportional regulating valve and the operating frequency of the liquid pump. Step 7, Linkage Control: The control unit controls the oil separator solenoid valve by combining the opening and closing status of the oil supply solenoid valve and the oil level signal time. Step 8, Load Adaptation: The control unit, in conjunction with the compressor's load status, adjusts the output pressure of the liquid extraction pump and the proportional control valve; Step 9, Unit Shutdown: The control unit completes the shutdown operation by sequentially closing the liquid extraction pump, liquid extraction solenoid valve, oil separator solenoid valve, and oil supply solenoid valve.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: 1. This invention provides independent power through a liquid extraction pump, eliminating dependence on the suction and discharge pressure difference of the compressor, and can still return oil efficiently under low load conditions; the load judgment module can automatically adjust the pressure of the liquid extraction pump and the opening of the regulating valve to adapt to the oil return needs of the unit under all operating conditions, and solve the problem of low oil return efficiency of traditional ejector pumps under low load. 2. This invention integrates multiple monitoring components and control units to monitor parameters such as flow rate, temperature, liquid level, and pressure in real time, and automatically adjusts the actions of the actuators to achieve dynamic balance in the oil return process; it avoids the drawbacks of manual adjustment, prevents poor oil return effect or excessive liquid refrigerant from entering the compressor, and improves operational safety. 3. The return oil tank in this invention integrates heating, filtration, liquid level and pressure control functions. With the linkage control logic, it can automatically start and stop the liquid extraction, oil supply and oil separation device, and respond quickly in case of abnormal oil level or pressure exceeding the limit. At the same time, it has orderly control during shutdown and startup, which solves the problems of single function and lack of convenient rescue measures in traditional methods. 4. In summary, this invention integrates multiple functions, not only achieving efficient oil return under all operating conditions through the liquid extraction pump and load judgment module, and achieving dynamic balance of oil return by integrating multiple monitoring components and control units, but also realizing automatic adjustment under all operating conditions, rapid response to abnormal situations, and orderly control during shutdown and startup stages by leveraging the heating, filtration and other functions integrated in the oil return tank and the linkage control logic. This effectively solves a variety of problems existing in traditional methods and comprehensively improves the unit's operating efficiency and safety. Attached Figure Description

[0015] Figure 1 This is a structural diagram of the present invention; Figure 2 This is a control flowchart of the control unit in this invention; Figure 3 This is a schematic diagram of the planar structure of the oil return tank in this invention.

[0016] Figure label: 1. Compressor; 2. Oil separator; 3. Condenser; 4. Throttling device; 5. Evaporator; 6. Liquid extraction filter; 7. Liquid extraction pump; 8. Liquid-taking solenoid valve; 9. Check valve; 10. Return oil tank; 101. Oil supply port; 102. Oil inlet; 103. Liquid inlet; 104. Exhaust port; 105. Tank body; 106. Filter screen; 107. Upper baffle; 108. Lower baffle; 109. Baffle notch; 110. Oil heater; 111. Liquid level sensor; 112. Pressure sensor; 11. Oil separator solenoid valve; 12. Oil supply filter; 13. Oil supply solenoid valve; 14. Oil flow switch; 15. Oil temperature sensor; 16. Proportional regulating valve. Detailed Implementation

[0017] 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.

[0018] like Figure 1 and Figure 3 As shown, this embodiment of the invention provides a control system for a direct expansion evaporator, including a control unit, a refrigerant circulation loop, and an oil return control component integrated in the refrigerant circulation loop. The refrigerant circulation loop is sequentially connected to a compressor 1, an oil separator 2, a condenser 3, a throttling device 4, and an evaporator 5. The oil return control component includes an execution component, a monitoring component, and connecting pipelines. The execution component includes a liquid extraction filter 6, a liquid extraction pump 7, a liquid extraction solenoid valve 8, a check valve 9, an oil return tank 10, an oil separation solenoid valve 11, an oil supply filter 12, an oil supply solenoid valve 13, a proportional regulating valve 16, and an oil heater 110. The monitoring component includes an oil flow switch 14, an oil temperature sensor 15, a liquid level sensor 111, and a pressure sensor 112. The liquid level sensor 111 and the pressure sensor 112 are installed on the oil return tank 10. The control unit is electrically connected to the liquid level sensor 111 and receives the oil level signal in the oil return tank 10. When the oil level is higher than the upper threshold, the control unit closes the liquid extraction solenoid valve 8 and the oil separation solenoid valve 11. If the oil level is below the lower threshold, the control unit simultaneously opens the liquid extraction solenoid valve 8 and the oil separator solenoid valve 11, and increases the operating power of the liquid extraction pump 7. The control unit is electrically connected to the actuator and monitoring components, receives signals from the monitoring components, and controls the actuator to achieve multi-functional oil return control of the refrigeration unit. The control unit is electrically connected to the pressure sensor 112 to receive the pressure signal in the return oil tank 10. If the pressure is higher than the safety threshold, the control unit increases the opening of the proportional regulating valve 16. If the pressure is lower than the minimum working pressure, the control unit decreases the opening of the proportional regulating valve 16 and reduces the operating frequency of the liquid extraction pump 7. The control unit is linked with the liquid extraction pump 7 and the liquid extraction solenoid valve 8 for control. During the unit startup process, the control unit opens the liquid extraction solenoid valve 8. After the liquid extraction solenoid valve 8 opens for 3-5 seconds, the control unit starts the liquid extraction pump 7, which extracts the liquid through a filter. The refrigerant filtered by the filter 6, carrying lubricating oil, enters the return oil tank 10 through the one-way valve 9. When the unit performs a shutdown operation, the control unit issues a command to shut down the liquid extraction pump 7. After the liquid extraction pump 7 shuts down for 10-15 seconds, the control unit closes the liquid extraction solenoid valve 8. The control unit is linked with the oil separator solenoid valve 11 and the oil supply solenoid valve 13 for control. When the oil supply solenoid valve 13 is open, the control unit adjusts the opening of the oil separator solenoid valve 11 according to the oil level signal. When the oil supply solenoid valve 13 is closed, the control unit simultaneously closes the oil separator solenoid valve 11. The control unit is equipped with a load judgment module. When the load judgment module detects that the compressor 1 is under low load, the control unit increases the output pressure of the liquid extraction pump 7 and increases the opening of the proportional regulating valve 16 to maintain the effective power of the return oil system. When the compressor 1 returns to its rated load, the control unit automatically returns to the normal control parameters. The return oil tank 10 is connected to the evaporator 5, oil separator 2, and compressor 1 via pipelines. The oil inlet of the return oil tank 10 is connected to the liquid outlet of the evaporator 5 via a pipeline connected in sequence to a one-way valve 9, a liquid extraction solenoid valve 8, a liquid extraction pump 7, and a liquid extraction filter 6. The oil inlet of the return oil tank 10 is connected to the oil separator solenoid valve 11 via a pipeline and then to the oil outlet of the oil separator 2. The oil supply end of the return oil tank 10 is connected to the oil supply filter 12, an oil supply solenoid valve 13, and an oil flow switch 14 via a pipeline and then to the oil inlet of the compressor 1. The exhaust port of the return oil tank 10 is connected to the air inlet of the evaporator 5 via a pipeline connected to a proportional regulating valve 16. The control unit is electrically connected to the oil flow switch 14 and receives the lubricating oil flow signal from the oil flow switch 14. When the flow rate is lower than a set threshold, the control unit increases the proportional flow rate. The control unit adjusts the opening of the regulating valve 16 and increases the operating frequency of the liquid pump 7 until the flow rate reaches the preset threshold. The control unit is electrically connected to the oil temperature sensor 15, which is installed on the pipeline between the oil flow switch 14 and the compressor 1. The oil temperature sensor 15 receives the lubricating oil temperature signal. If the temperature is lower than the set value, the control unit starts the oil heater 110 built into the return oil tank 10 and closes the oil supply solenoid valve 13. If the temperature reaches the set value, the control unit closes the oil heater 110 and opens the oil supply solenoid valve 13. The oil separator solenoid valve 11 is located between the oil inlet 102 and the oil separator 2. The oil supply filter 12, the oil supply solenoid valve 13, and the oil flow switch 14 are connected in sequence. The oil temperature sensor 15 is installed on the pipeline between the oil flow switch 14 and the compressor 1. The proportional regulating valve 16 is connected to the air inlet of the evaporator 5. The return oil tank 10 includes a tank body 105, an oil supply port 101, an oil inlet port 102, and a liquid inlet port 103. A one-way valve 9 is located on the connecting pipeline between the liquid extraction solenoid valve 8 and the liquid inlet port 103. The oil supply port 101 is located below the oil inlet port 102. A 104 is provided on the top of the tank body 105. A liquid level sensor 111 runs through the entire tank body 105 from top to bottom. Inside the tank body 105, a filter screen 106, an upper baffle 107, and a lower baffle 108 are arranged sequentially from top to bottom. The liquid inlet port 103 and the oil inlet port 102 are set at a height higher than the upper baffle 107. Both the lower baffle 108 and the upper baffle 107 are provided with baffle notches 109. An oil heater 110 is located at the bottom of the tank body 105, below the liquid inlet port 103.

[0019] Combination Figure 3 As shown, the present invention also proposes a control method for a multi-functional oil return system of a refrigeration unit, the method comprising the following steps: Step 1: System initialization: The control unit starts and detects the initial signals of the oil flow switch 14, oil temperature sensor 15, liquid level sensor 111 and pressure sensor 112, and puts all actuators in the off state. Step 2, Unit Start-up: The control unit first opens the liquid extraction solenoid valve 8, and after a delay of 3-5 seconds, starts the liquid extraction pump 7. After the liquid extraction pump 7 runs stably, according to the initial oil level of the return oil tank 10 fed back by the liquid level sensor 111, the oil separator solenoid valve 11 and the oil supply solenoid valve 13 are opened. Step 3: The control unit receives the lubricating oil flow signal from the oil flow switch 14 in real time. When the flow rate is lower than the set threshold, the opening of the proportional regulating valve 16 is increased and the operating frequency of the liquid pump 7 is increased until the flow rate reaches the set range. Step 4, Oil Temperature Adjustment: The control unit receives the temperature signal from the oil temperature sensor 15. When the temperature is lower than the set value, the oil heater 110 is started and the oil supply solenoid valve 13 is closed; when the temperature reaches the set value, the oil heater 110 is closed and the oil supply solenoid valve 13 is opened. Step 5, Oil Level Adjustment: The control unit, based on the oil level in the return oil tank 10 monitored by the liquid level sensor 111, closes the liquid extraction solenoid valve 8 and the oil separation solenoid valve 11 when the oil level is higher than the upper threshold; and opens the liquid extraction solenoid valve 8 and the oil separation solenoid valve 11 simultaneously when the oil level is lower than the lower threshold, and increases the operating power of the liquid extraction pump 7. Step 6, Pressure Regulation: The control unit receives the pressure signal from the pressure sensor 112 in the return oil tank 10. When the pressure is higher than the safety threshold, the opening of the proportional regulating valve 16 is increased; when the pressure is lower than the minimum working pressure, the opening of the proportional regulating valve 16 is decreased and the operating frequency of the liquid pump 7 is reduced. Step 7, Linkage Control: When the oil supply solenoid valve 13 is open, the control unit adjusts the opening of the oil separator solenoid valve 11 according to the oil level signal; when the oil supply solenoid valve 13 is closed, the oil separator solenoid valve 11 is closed synchronously. Step 8, Load Adaptation: The control unit detects the operating condition of the compressor 1 through the built-in load judgment module. When the control unit detects that the compressor 1 is under low load, it increases the output pressure of the liquid pump 7 and increases the opening of the proportional regulating valve 16; when the compressor 1 returns to the rated load, it returns to the normal parameters. Step 9, Unit Shutdown: The control unit first shuts down the liquid extraction pump 7, and after a delay of 10-15 seconds, shuts down the liquid extraction solenoid valve 8, and simultaneously shuts down the oil separator solenoid valve 11 and the oil supply solenoid valve 13 to complete the shutdown of the oil return system.

[0020] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A multi-functional oil return control system for a refrigeration unit, characterized in that, It includes a control unit, a refrigerant circulation loop, and an oil return control component integrated in the refrigerant circulation loop; the refrigerant circulation loop is sequentially connected to a compressor (1), an oil separator (2), a condenser (3), a throttling device (4), and an evaporator (5). The oil return control component includes an execution component, a monitoring component, and connecting pipelines. The execution component includes a liquid extraction filter (6), a liquid extraction pump (7), a liquid extraction solenoid valve (8), a check valve (9), an oil return tank (10), an oil separator solenoid valve (11), an oil supply filter (12), an oil supply solenoid valve (13), a proportional regulating valve (16), and an oil heater (110). The monitoring components include an oil flow switch (14), an oil temperature sensor (15), a liquid level sensor (111), and a pressure sensor (112). The control unit is electrically connected to the execution component and the monitoring component, receives signals from the monitoring component and controls the action of the execution component to realize multi-functional oil return control of the refrigeration unit.

2. The multi-functional oil return control system for a refrigeration unit according to claim 1, characterized in that, The return oil tank (10) is connected to the evaporator (5), oil separator (2), and compressor (1) respectively via pipelines; Among them, the oil inlet of the return oil tank (10) is connected to the one-way valve (9), the liquid solenoid valve (8), the liquid pump (7), and the liquid filter (6) in sequence through the pipeline and then connected to the liquid outlet of the evaporator (5). The oil inlet of the return oil tank (10) is connected to the oil separator solenoid valve (11) via a pipeline and then connected to the oil outlet of the oil separator (2); The oil supply end of the return oil tank (10) is connected to the oil supply filter (12), oil supply solenoid valve (13), and oil flow switch (14) in sequence through pipelines, and then connected to the oil inlet end of the compressor (1). The exhaust port of the return oil tank (10) is connected to the air inlet of the evaporator (5) via a pipeline connected to a proportional regulating valve (16).

3. The multi-functional oil return control system for a refrigeration unit according to claim 1, characterized in that, The control unit is electrically connected to the oil flow switch (14) and receives the lubricating oil flow signal fed back by the oil flow switch (14); When the flow rate is lower than the set threshold, the control unit increases the opening of the proportional regulating valve (16) and increases the operating frequency of the liquid pump (7) until the flow rate reaches the preset threshold. The control unit is electrically connected to the oil temperature sensor (15), which is installed on the pipeline between the oil flow switch (14) and the compressor (1) to receive the lubricating oil temperature signal. When the temperature is lower than the set value, the control unit starts the oil heater (110) built into the return oil tank (10) and closes the oil supply solenoid valve (13). If the temperature reaches the set value, the control unit shuts off the oil heater (110) and opens the oil supply solenoid valve (13).

4. The multi-functional oil return control system for a refrigeration unit according to claim 1, characterized in that, The liquid level sensor (111) and pressure sensor (112) are installed on the return oil tank (10). The control unit is electrically connected to the liquid level sensor (111) and receives the oil level signal in the return oil tank (10). When the oil level is higher than the upper limit threshold, the control unit closes the liquid extraction solenoid valve (8) and the oil separator solenoid valve (11). If the oil level is below the lower limit threshold, the control unit simultaneously opens the liquid extraction solenoid valve (8) and the oil separator solenoid valve (11), and increases the operating power of the liquid extraction pump (7).

5. The multi-functional oil return control system for a refrigeration unit according to claim 1, characterized in that, The control unit is electrically connected to the pressure sensor (112) and is used to receive the pressure signal in the return oil tank (10); If the pressure exceeds the safety threshold, the control unit increases the opening of the proportional regulating valve (16); If the pressure is lower than the minimum working pressure, the control unit reduces the opening of the proportional regulating valve (16) and reduces the operating frequency of the liquid pump (7).

6. The multi-functional oil return control system for a refrigeration unit according to claim 1, characterized in that, The control unit is linked to the liquid pump (7) and the liquid solenoid valve (8) for control. During the unit startup process, the control unit opens the liquid extraction solenoid valve (8). After the liquid extraction solenoid valve (8) is open for 3-5 seconds, the control unit starts the liquid extraction pump (7). The refrigerant filtered by the liquid extraction filter (6) carries the lubricating oil through the one-way valve (9) into the return oil tank (10). When the unit performs a shutdown operation, the control unit issues a command to shut down the liquid extraction pump (7). After the liquid extraction pump (7) is shut down for 10-15 seconds, the control unit shuts down the liquid extraction solenoid valve (8).

7. A multi-functional oil return control system for a refrigeration unit according to claim 3, characterized in that, The control unit is linked with the oil separator solenoid valve (11) and the oil supply solenoid valve (13) for control. When the oil supply solenoid valve (13) is opened, the control unit adjusts the opening degree of the oil separator solenoid valve (11) according to the oil level signal; When the oil supply solenoid valve (13) is closed, the control unit simultaneously closes the oil separator solenoid valve (11).

8. A multi-functional oil return control system for a refrigeration unit according to claim 1, characterized in that, The control unit is equipped with a load determination module; The load judgment module detects that the compressor (1) is under low load. The control unit increases the output pressure of the liquid pump (7) and increases the opening of the proportional regulating valve (16) to maintain the effective power of the oil return system. When the compressor (1) returns to its rated load, the control unit automatically reverts to the normal control parameters.

9. A multi-functional oil return control system for a refrigeration unit according to claim 1, characterized in that, The return oil tank (10) includes a tank body (105), an oil supply port (101), an oil inlet (102), and a liquid inlet (103). The one-way valve (9) is located on the connecting pipeline between the liquid-taking solenoid valve (8) and the liquid inlet (103). The oil supply port (101) is located below the oil inlet (102). The top of the tank body (105) is provided with a (104). The liquid level sensor (111) runs through the entire tank body (105) from top to bottom. 5) The tank is provided with a filter screen (106), an upper baffle (107) and a lower baffle (108) from top to bottom. The liquid inlet (103) and the oil inlet (102) are set at a height higher than the upper baffle (107). The lower baffle (108) and the upper baffle (107) are both provided with baffle notches (109). The oil heater (110) is set at the bottom of the tank (105) and is located below the liquid inlet (103). The oil separator solenoid valve (11) is located between the oil inlet (102) and the oil separator (2). The oil supply filter (12), the oil supply solenoid valve (13), and the oil flow switch (14) are connected in sequence. The oil temperature sensor (15) is installed on the pipeline between the oil flow switch (14) and the compressor (1). The proportional regulating valve (16) is connected to the air inlet of the evaporator (5).

10. A control method for a multi-functional oil return system of a refrigeration unit according to any one of claims 1 to 9, characterized in that, The control method includes the following steps: Step 1, System Initialization: The control unit starts and detects the initial signals of the oil flow switch (14), oil temperature sensor (15), liquid level sensor (111) and pressure sensor (112), and puts all actuators in the off state; Step 2, Unit Start-up: The control unit first opens the liquid extraction solenoid valve (8), and after a delay of 3-5 seconds, starts the liquid extraction pump (7). Once it is running stably, the oil separator solenoid valve (11) and the oil supply solenoid valve (13) are opened according to the initial oil level in the return oil tank. Step 3, Flow rate adjustment: The control unit receives the signal from the oil flow switch (14) to adjust the flow rate; Step 4, oil temperature regulation: The control unit receives the temperature data collected by the oil temperature sensor (15), compares it with the temperature set value, and realizes the opening and closing of the oil heater (110) and the oil supply solenoid. Step 5, oil level adjustment: The control unit realizes the opening and closing of the liquid-taking solenoid valve (8) and the oil-separating solenoid valve (11) and the power adjustment based on the oil level data monitored by the liquid level sensor (111). Step 6, Pressure Regulation: The control unit is used to receive the signal from the pressure sensor (112) and to adjust the opening of the proportional regulating valve (16) and the operating frequency of the liquid pump (7); Step 7, Linkage Control: The control unit controls the oil separator solenoid valve (11) in conjunction with the opening and closing status of the oil supply solenoid valve (13) and the oil level signal time. Step 8, Load Adaptation: The control unit, in conjunction with the load status of the compressor (1), adjusts the output pressure of the liquid pump (7) and the proportional regulating valve (16); Step 9, Unit Shutdown: The control unit completes the sequential shutdown of the liquid pump (7), liquid solenoid valve (8), oil separator solenoid valve (11) and oil supply solenoid valve (13) to complete the shutdown operation.

Images