Refrigeration unit control method, control system, air conditioner and control device

Abstract

The present invention provides a control method for a refrigeration unit, a control system, an air conditioner and a control device, which relates to the technical field of air conditioners, and solves the technical problem in the prior art that a direct-through oil separator returns oil by differential pressure. When the unit operates at a high differential pressure, the lubricating oil in the oil separator quickly returns to the compressor, which is likely to cause oil return and gas stringing. The control method includes the following: detecting the oil temperature T of the oil return pipe 回油 ; judging the level of the oil temperature T of the oil return pipe 回油 ; if it is judged that the oil temperature T of the oil return pipe 回油 is high, controlling the oil return solenoid valve to close; if it is judged that the oil temperature T of the oil return pipe 回油 is low, controlling the oil return solenoid valve to open. The present invention is used to ensure the reliability of oil return during the operation of the unit at a high differential pressure, so as to avoid oil return and gas stringing as much as possible and improve the stability of the unit.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioners, and in particular to a refrigeration unit control method, a control system, an air conditioner and a control device. Background Art

[0002] At present, low-temperature refrigeration units are used in low-temperature cold storage. The storage temperature is generally -20℃ or lower, and the evaporation temperature reaches below -30℃. As the evaporation temperature decreases, the viscosity of the oil increases, and the reliability of oil return is the key concern of the low-temperature unit. In order to avoid the difficulty of oil return on the evaporation side of the system, an oil separator is generally added to the high-pressure side during the system design process to ensure that the oil discharged from the compressor can smoothly return to the compressor, effectively preventing the compressor oil from being discharged in large quantities to the low-pressure side of the system. Although this method can ensure the reliability of oil return of the unit under normal working conditions. However, for units under harsh working conditions such as high pressure difference conditions and defrosting conditions, there are still the following problems that cannot be improved:

[0003] 1. Generally, the return oil on the high-pressure side returns to the compressor suction pipe. The return oil temperature is generally 50-100°C higher than the suction temperature. During the unit oil return process, the compressor suction port temperature rises, the suction specific volume increases, and the suction mass flow rate decreases, which leads to a decrease in the refrigeration capacity of the low-temperature unit;

[0004] 2. When the low-temperature unit completes defrosting and starts refrigeration again, a large amount of liquid on the evaporation side enters the compressor, causing the compressor oil discharge rate to increase. The compressor lubricating oil will be discharged from the outside of the compressor along with the refrigerant, causing the compressor oil discharge volume to increase during the compressor defrosting switching process, posing a safety hazard;

[0005] 3. When the unit is operating under high pressure difference conditions, the straight-through oil separator returns oil by pressure difference. Due to the large pressure difference at this time, the lubricating oil in the oil separator quickly returns to the compressor, causing oil return and air cross-talk, which further leads to high suction temperature and high exhaust temperature of the unit, causing certain safety hazards. Summary of the invention

[0006] The purpose of the present invention is to provide a refrigeration unit control method, control system, air conditioner and control device, which solves the technical problem that the direct oil separator in the prior art relies on the pressure difference to return oil. When the unit is running with a high pressure difference, the lubricating oil in the oil separator quickly returns to the compressor, which easily causes oil return and gas contamination. The preferred technical solutions among the many technical solutions provided by the present invention can produce many technical effects as described below.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a refrigeration unit control method, comprising the following contents: detecting the oil temperature T of the oil return pipe 回油 ; Determine the oil temperature T of the return oil pipe 回油Temperature; if the oil temperature of the return oil pipe is T 回油 If the oil temperature in the oil return pipe is T 回油 If the temperature is low, the oil return solenoid valve is controlled to open.

[0009] Furthermore, if T 回油 <T 压油 +ΔT, then judge the oil temperature of the oil pipe T 回油 is low temperature; if T 回油 ≥T 压油 +ΔT, then judge the oil temperature of the oil pipe T 回油 is high temperature; where ΔT is the system preset value, T 压油 The oil temperature of the compressor to be detected.

[0010] Furthermore, when judging the oil temperature T of the oil return pipe 回油 Before the temperature is high or low, first detect the compressor startup time. If the compressor startup time is T1, then judge the oil temperature of the return oil pipe T 回油 The temperature is high or low; among them, T1 is the system preset value.

[0011] Furthermore, the refrigeration unit control method further includes the following contents: determining the suction superheat SH of the compressor; 设定 The superheat deviation e is obtained; and the opening and closing degree of the electronic expansion valve is controlled according to the superheat deviation e.

[0012] Furthermore, the suction superheat SH and the superheat setting value T 设定 Get the superheat deviation e, which includes the following: When the ambient temperature ≥ T2 and the cold storage temperature ≤ T3, the superheat deviation e = suction superheat SH-superheat setting value T 设定 *D; When the ambient temperature is less than T2 or the cold storage temperature is greater than T3, the superheat deviation e = suction superheat SH - superheat setting value T 设定 .

[0013] The present invention provides a control system for implementing the refrigeration unit control method, comprising a compressor, an oil separator and a gas-liquid separator, wherein the oil separator and the gas-liquid separator are both connected to the compressor, an oil return pipeline is arranged between the oil separator and the compressor, and a partial section of the oil return pipeline is arranged around the outer surface of the gas-liquid separator.

[0014] Furthermore, the oil return capillary on the oil return pipeline is wound around the outer surface of the gas-liquid separator and is close to the lower end of the gas-liquid separator.

[0015] Furthermore, an oil return solenoid valve and an oil return temperature sensor are arranged on the oil return pipeline, and an oil pressure temperature sensor is arranged at the bottom of the compressor. The oil return solenoid valve, the oil return temperature sensor and the oil pressure temperature sensor are all connected to the controller of the control system.

[0016] The present invention provides an air conditioner, comprising the control system.

[0017] The present invention provides a control device, comprising: a detection module for detecting the oil temperature of the oil return pipe; a judgment module for judging the oil temperature T of the oil return pipe. 回油 The temperature; the control module is used to control the switch of the oil return solenoid valve.

[0018] The beneficial effects of the present invention are as follows: the present invention detects the oil temperature T of the oil return pipe 回油 , to control the switch of the oil return solenoid valve. 回油 When it is high temperature, it is considered that high temperature refrigerant has entered the oil return pipe, causing the oil temperature to rise. Therefore, in order to prevent high temperature gas from entering the compressor suction port, the oil return solenoid valve is controlled to close; when it is judged that the oil temperature of the oil return pipe is T 回油 When the temperature is low, it is considered that there is lubricating oil in the oil separator and no high-temperature refrigerant enters the oil return pipe, so the oil return solenoid valve is controlled to open. By controlling the oil return solenoid valve in the above way, the oil return reliability of the unit during high pressure difference operation is guaranteed to avoid oil return gas as much as possible and improve the stability of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 is a schematic diagram of a control system provided by an embodiment of the present invention;

[0021] Figure 2 It is a flow chart of a refrigeration unit control method provided by an embodiment of the present invention.

[0022] In the figure, 1- compressor; 2- oil separator; 3- fin heat exchanger; 4- evaporator; 5- gas-liquid separator; 6- four-way reversing valve; 7- drying filter; 8- electronic expansion valve; 9- suction stop valve; 10- liquid supply stop valve; 11- capillary tube; 12- filter; 13- solenoid valve; 14- oil return solenoid valve; 15- one-way valve; 16- oil pressure temperature sensor; 17- oil return temperature sensor; 18- suction temperature sensing package and suction pressure sensor; 19- exhaust temperature sensor. DETAILED DESCRIPTION

[0023] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0024] Embodiment 1:

[0025] In order to avoid the difficulty of oil return on the evaporation side of the system, an oil separator 2 is generally added on the high-pressure side of the refrigeration system to ensure that the oil discharged from the compressor 1 can smoothly return to the compressor 1, effectively preventing the oil from the compressor 1 from being discharged to the low-pressure side of the system in large quantities. Since the straight-through oil separator relies on the pressure difference to return the oil, the greater the pressure difference, the faster the oil return. When the oil return volume is greater than the oil discharge volume of the compressor, there will be no lubricating oil in the oil separator 2. Due to the pressure difference, the high-temperature and high-pressure gas will enter the compressor suction port through the oil return pipeline, resulting in high suction temperature and high exhaust temperature of the compressor, causing oil return gas, which further leads to high suction temperature and high exhaust temperature of the unit, affecting the reliability of the unit operation.

[0026] Based on the above problems, the present invention provides a refrigeration unit control method, including the following contents: detecting the oil temperature T of the oil return pipe 回油 ; Determine the oil temperature T of the return oil pipe 回油 Temperature; if the oil temperature of the return oil pipe is T 回油 If the oil temperature in the oil return pipe is T 回油 If the temperature is low, the oil return solenoid valve 14 is controlled to open.

[0027] When there is gas cross-talk with the oil return pipe of the oil separator 2, the return oil temperature will be too high. 回油 , to control the switch of the oil return solenoid valve 14. 回油 When the oil temperature in the oil return pipe is T, it is considered that high-temperature refrigerant has entered the oil return pipe, causing the oil temperature to rise. Therefore, in order to prevent high-temperature gas from entering the suction port of the compressor 1, the oil return solenoid valve 14 is controlled to be closed.回油 When the temperature is low, it is considered that there is lubricating oil in the oil separator 2, and no high-temperature refrigerant enters the oil return pipe, so the oil return solenoid valve 14 is controlled to open. By controlling the oil return solenoid valve 14 in the above method, the oil return reliability of the unit during high pressure difference operation is guaranteed to avoid oil return gas as much as possible, thereby improving the stability of the unit.

[0028] Here, it should be noted that the existing control of the oil return solenoid valve usually adopts a fixed cycle to open, that is, the oil return solenoid valve is controlled to open for a preset time at each set time interval, which is prone to oil return gas leakage.

[0029] About the oil temperature T of the oil return pipe 回油 The judgment of high temperature and low temperature can be as follows: If T 回油 <T 压油 +ΔT, then judge the oil temperature of the return oil pipe T 回油 is low temperature; if T 回油 ≥T 压油 +ΔT, then judge the oil temperature of the return oil pipe T 回油 is high temperature; where ΔT is the system preset value, T 压油 The oil temperature of the compressor to be detected.

[0030] See also Figure 1 The oil return pipe is provided with an oil return temperature sensor 17, which is used to detect the oil temperature T 回油 A pressure oil temperature sensor 16 is provided at the bottom of the compressor, and the pressure oil temperature sensor 16 is used to detect the compressor oil temperature T 压油 When T 回油 <T 压油 +ΔT, then judge the oil temperature of the return oil pipe T 回油 is low temperature; when T 回油 ≥T 压油 +ΔT, then judge the oil temperature of the return oil pipe T 回油 For high temperature.

[0031] Regarding ΔT, it is the preset value of the system. Through experiments, a reasonable ΔT value can be obtained. The oil pressure temperature sensor 16 detects the oil temperature at the bottom of the compressor. Since the lubricating oil at the bottom of the compressor has not been compressed, there is generally a temperature difference of about 50°C with the oil temperature at the return oil pipe. When the system pressure difference is too large and the return oil pipe has cross-flow, the temperature detected by the return oil pipe is close to the exhaust temperature (generally above 105°C). At this time, T 回油 With T 压油 There is a temperature difference of more than 60°C. Therefore, in order to ensure the detection accuracy and avoid misjudgment, the recommended △T value is 10-60°C.

[0032] In addition, when judging the oil temperature T of the return oil pipe 回油Before determining the temperature, first check the compressor startup time. If the compressor startup time is T1, then determine the oil temperature of the return oil pipe T 回油 The temperature is high or low; among them, T1 is the system preset value, and T1 may be different for different refrigeration units.

[0033] Embodiment 2:

[0034] Different from the first embodiment, the refrigeration unit control method further includes the following steps: determining the suction superheat SH of the compressor; determining the suction superheat SH according to the suction superheat SH and the superheat setting value T 设定 The superheat deviation e is obtained; and the opening and closing degree of the electronic expansion valve is controlled according to the superheat deviation e.

[0035] See also Figure 1 The unit has an air suction temperature sensor and an air suction pressure sensor 18, which detect the air suction temperature and air suction pressure. The air suction superheat SH = air suction temperature - evaporation temperature, where the evaporation temperature is the saturation temperature corresponding to the air suction pressure. Based on the air suction superheat SH and the superheat setting value T 设定 The superheat deviation e is obtained; the opening and closing degree of the electronic expansion valve 8 is controlled according to the superheat deviation e, that is, during the refrigeration process, the opening degree of the electronic expansion valve 8 is adjusted by the PID adjustment unit according to the superheat deviation e to adjust the heat, so as to ensure the refrigeration effect of the evaporator.

[0036] About the suction air superheat SH and superheat setting value T 设定 Get the superheat deviation e, which includes the following: When the ambient temperature ≥ T2 and the cold storage temperature ≤ T3, the superheat deviation e = suction superheat SH-superheat setting value T 设定 *D; When the ambient temperature is less than T2 or the cold storage temperature is greater than T3, the superheat deviation e = suction superheat SH - superheat setting value T 设定 .

[0037] Regarding the superheat deviation e, when the calculated superheat deviation is a negative value, the number of steps of change of the electronic expansion valve calculated according to the PID formula for electronic expansion valve regulation is also a negative value, that is, the expansion valve is closed; conversely, if the calculated result is a positive value, it means that the expansion valve needs to be opened wider.

[0038] Regarding D, it is the attenuation coefficient, and the value of D is less than 1. When the ambient temperature is ≥ T2 and the cold storage temperature is ≤ T3, the pressure on the low-pressure side drops suddenly due to the low temperature of the inner ring, and the pressure on the high-pressure side remains high due to the high temperature of the outer ring. At this time, the high-low pressure difference is too large, which is easy to cause oil return gas. In order to speed up the system adjustment speed and avoid the system from running with liquid, the superheat setting value T 设定 Multiply by a factor less than 1, that is, reduce the system superheat. When the reduction amplitude is reduced to ensure that the system still has T 设定低When the superheat is ℃, the value of D is T 设定低 / T 设定 For example, when the amplitude is reduced to ensure that the system still has an overheat of about 3°C, that is, D≈3 / T 设定 .

[0039] The superheat deviation e and the opening of the electronic expansion valve 8 are prior art and will not be elaborated here. Usually, the electronic expansion valve 8 is adjusted every T seconds, and the controller calculates the system's suction superheat (suction pressure and evaporator outlet temperature) every 1 second, calculates the average suction superheat of the system in the first 5 seconds, and compares the average suction superheat with the superheat setting value T 设定 Get the superheat deviation e.

[0040] Embodiment 3:

[0041] The present invention provides a control system, comprising a compressor 1, an oil separator 2 and a gas-liquid separator 5, wherein the oil separator 2 and the gas-liquid separator 5 are both connected to the compressor 1, an oil return pipeline is arranged between the oil separator 2 and the compressor 1, and a part of the oil return pipeline is wound around the outer surface of the gas-liquid separator 5. Preferably, the oil return capillary on the oil return pipeline is wound around the outer surface of the gas-liquid separator 5 and close to the lower end of the gas-liquid separator.

[0042] The oil return capillary is evenly wound and fixed on the lower surface of the gas-liquid separator 5. When the unit re-enters the refrigeration operation after the defrosting operation is completed, the liquid in the evaporator 4 after defrosting enters the gas-liquid separator 5, resulting in a large amount of liquid refrigerant in the gas-liquid separator 5. It is easy for liquid refrigerant to enter the compressor 1. If the unit is operated with liquid for a long time (that is, liquid refrigerant enters the compressor 1), it will cause the unit to leak oil, thereby causing compressor wear. The present invention can accelerate the rapid evaporation of liquid in the gas-liquid separator 5 through heat exchange between the oil return capillary and the gas-liquid separator 5, avoiding compressor wear caused by long-term operation of the compressor with liquid, and at the same time can fully reduce the return oil temperature, avoiding excessively high suction temperature, increasing suction specific volume, and reducing suction flow rate, which causes the unit's refrigeration capacity to decrease.

[0043] The oil return solenoid valve 14 and the oil return temperature sensor 17 are arranged on the oil return pipe, and the oil pressure temperature sensor 16 is arranged at the bottom of the compressor 1. The oil return solenoid valve 14, the oil return temperature sensor 17 and the oil pressure temperature sensor 16 are all connected to the controller of the control system. The oil return temperature sensor 17 is arranged on the oil return pipe, and the oil return temperature sensor 17 is used to detect the oil temperature T 回油 A pressure oil temperature sensor 16 is provided at the bottom of the compressor, and the pressure oil temperature sensor 16 is used to detect the compressor oil temperature T 压油 The control device controls the switch status of the oil return solenoid valve 14 by analyzing the signals detected by the oil return temperature sensor 17 and the oil pressure temperature sensor 16 .

[0044] See also Figure 1 , which shows the principle diagram of the control system. The control system includes compressor 1, oil separator 2, fin heat exchanger 3, evaporator 4, gas-liquid separator 5, four-way reversing valve 6, dry filter 7, electronic expansion valve 8, suction stop valve 9, liquid supply stop valve 10, capillary 11, filter 12, solenoid valve 13, return oil solenoid valve 14, check valve 15, oil pressure temperature sensor 16, return oil temperature sensor 17, suction temperature sensor and suction pressure sensor 18, exhaust temperature sensor 19. The main operating principles are as follows:

[0045] (1) When the unit is in refrigeration operation, the four-way reversing valve 6 is in the power-off state, the DC of the four-way reversing valve 6 is connected and the ES is connected, the high-temperature and high-pressure gas discharged from the compressor 1 passes through the oil separator 2, and after the oil and gas separation in the oil separator 2, the high-temperature and high-pressure refrigerant enters the fin heat exchanger 3 through the four-way reversing valve C tube for condensation, and the refrigeration oil separated by the oil separator 2 passes through the oil return solenoid valve 14 and the oil return capillary tube and enters the suction pipe and returns to the compressor 1, and the high-temperature and high-pressure liquid coming out of the fin heat exchanger 3 is throttled by the electronic expansion valve 8 to become a low-temperature and low-pressure two-phase flow gas-liquid mixture, passes through the evaporator 4 for heat exchange, becomes a low-pressure superheated gas, and then passes through the four-way reversing valve 6 and the gas separation and enters the compressor 1 to complete the refrigeration cycle;

[0046] (2) When the defrost is in operation, the four-way reversing valve 6 is energized, the DE of the four-way reversing valve 6 is connected and the SC is connected, the high-temperature and high-pressure gas discharged from the compressor 1 passes through the oil separator 2, and the high-temperature and high-pressure gas enters the evaporator 4 through the four-way reversing valve E tube for defrosting. The refrigerant oil separated by the oil separator 2 passes through the return oil solenoid valve 14 and the return oil capillary tube and enters the suction pipe and returns to the compressor 1. The defrosted liquid is throttled by the electronic expansion valve 8, and the low-temperature and low-pressure two-phase flow enters the fin heat exchanger 3 for evaporation and then passes through the SC of the four-way reversing valve 6 to enter the gas-liquid separator 5 and return to the compressor 1 to complete the entire defrost cycle.

[0047] An air conditioner includes the improved control system of the present invention. Since the control system has been described in detail above, it will not be described in detail here.

[0048] A control device comprises: a detection module for detecting the oil temperature of an oil return pipe; a judgment module for judging the oil temperature T of the oil return pipe 回油 The control module is used to control the switch of the oil return solenoid valve 14. The specific functions of the modules included in the control device have been specifically described in the control method of embodiment 1, and will not be repeated here.

[0049] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A refrigeration unit control method, characterized in that: It includes the following: Detect the oil temperature T of the oil return pipe 回油 ; Determine the oil temperature T of the oil return pipe 回油 The temperature If the oil temperature of the oil return pipe T 回油 If the temperature is high, the oil return solenoid valve is controlled to close; If the oil temperature of the oil return pipe T 回油 If the temperature is low, the oil return solenoid valve is controlled to open; If T 回油 <T 压油 +ΔT, then judge the oil temperature of the return oil pipe T 回油 is low temperature; if T 回油 ≥T 压油 +ΔT, then judge the oil temperature of the return oil pipe T 回油 For high temperature; Among them, ΔT is the system preset value, T 压油 The oil temperature of the compressor to be detected.

2. The refrigeration unit control method according to claim 1, characterized in that: In judging the oil temperature T of the oil return pipe 回油 Before the temperature is high or low, first detect the compressor startup time. If the compressor startup time is T1, then judge the oil temperature of the return oil pipe T 回油 The temperature Among them, T1 is the system preset value.

3. The refrigeration unit control method according to any one of claims 1 to 2, characterized in that: The refrigeration unit control method also includes the following contents: Determine the compressor suction superheat SH; Based on suction superheat SH and superheat setting value T 设定 Get the superheat deviation e; The opening and closing degree of the electronic expansion valve is controlled according to the superheat deviation e.

4. The refrigeration unit control method according to claim 3, characterized in that: The suction superheat SH and the superheat setting value T 设定 The superheat deviation e is obtained, which specifically includes the following contents: When the ambient temperature is ≥ T2 and the cold storage temperature is ≤ T3, the superheat deviation e = suction superheat SH-superheat setting value T 设定 *D; When the ambient temperature is less than T2 or the cold storage temperature is greater than T3, the superheat deviation e = suction superheat SH - superheat setting value T 设定 .

5. A control system for implementing the refrigeration unit control method according to any one of claims 1 to 4, comprising a compressor, an oil separator and a gas-liquid separator, wherein the oil separator and the gas-liquid separator are both connected to the compressor, and an oil return pipeline is arranged between the oil separator and the compressor, characterized in that: A partial section of the oil return pipeline is arranged around the outer surface of the gas-liquid separator.

6. The control system according to claim 5, characterized in that: The oil return capillary on the oil return pipeline is wound around the outer surface of the gas-liquid separator and is close to the lower end of the gas-liquid separator.

7. The control system according to claim 5, characterized in that: An oil return solenoid valve and an oil return temperature sensor are arranged on the oil return pipeline, and an oil pressure temperature sensor is arranged at the bottom of the compressor. The oil return solenoid valve, the oil return temperature sensor and the oil pressure temperature sensor are all connected to the controller of the control system.

8. An air conditioner, characterized in that: A control system comprising any one of claims 5-7.

9. A control device, characterized in that: include: Detection module, used to detect the oil temperature of the oil return pipe; Judgment module, used to judge the oil temperature T of the oil return pipe 回油 The temperature The control module is used to control the switch of the oil return solenoid valve.

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