Oil return control method and control device of multi-split air conditioner and multi-split air conditioner

Abstract

The invention relates to the technical field of air conditioners, and provides an oil return control method and device of a multi-split air conditioner and the multi-split air conditioner, the oil return control method of the multi-split air conditioner comprises a starting stage, in the starting stage, the outdoor environment temperature, the bottom oil temperature of a gas-liquid separator, the suction temperature of a compressor and the load rate of the multi-split air conditioner are obtained; the state of an electronic expansion valve is controlled according to the load rate and the bottom oil temperature, and the state of an electromagnetic valve is controlled according to the outdoor environment temperature, the bottom oil temperature and the suction temperature; wherein the state of the electromagnetic valve comprises opening and closing, and the state of the electronic expansion valve comprises initial opening and opening adjustment. When the lubricating oil is deposited in the gas-liquid separator, part of the lubricating oil at the bottom of the gas-liquid separator can flow back into the compressor by controlling the states of the electronic expansion valve and the electromagnetic valve, and the oil shortage fault of the compressor is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioners, and particularly to an oil return control method, a control device and a multi-connected air conditioner for a multi-connected air conditioner. Background Art

[0002] Due to the characteristics that the number of indoor and outdoor units and the output capacity of a multi-connected air conditioner can be freely adjusted according to requirements, the multi-connected air conditioner has been widely used nowadays. As the core component of the multi-connected air conditioner, the compressor is very vulnerable to insufficient system lubricating oil, which may cause damage to the compressor. In related technologies, a capillary tube is added to connect the bottom of the gas-liquid separator to the compressor suction pipe in the multi-connected system, and it is kept open during the system operation and standby states, so that the lubricating oil deposited at the bottom of the gas-liquid separator can flow back into the compressor along the compressor suction pipe. However, during the start-up stage and the operation stage under harsh working conditions of the multi-connected air conditioner, more lubricating oil in the system is likely to accumulate in the gas-liquid separator. When there is more lubricating oil, the compressor will experience an overloading phenomenon due to lack of oil inside, and long-term operation under the condition of lack of oil will cause damage to the compressor. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the related technologies. For this purpose, the present invention provides an oil return control method for a multi-connected air conditioner, which can make part of the lubricating oil at the bottom of the gas-liquid separator flow back into the compressor by controlling the states of an electronic expansion valve and a solenoid valve, thus avoiding the oil shortage fault of the compressor.

[0004] The present invention also provides an oil return control device for a multi-connected air conditioner.

[0005] The present invention also provides a multi-connected air conditioner.

[0006] According to the oil return control method for a multi-connected air conditioner provided by the first aspect embodiment of the present invention, the bottom of the gas-liquid separator is connected to the suction port of the compressor through a liquid discharge pipeline, and the liquid discharge pipeline is provided with a valve group composed of a solenoid valve and an electronic expansion valve in parallel. A first temperature sensor is provided upstream of the valve group, and a second temperature sensor is provided downstream of the valve group. The control method includes a start-up stage, and in the start-up stage:

[0007] Obtain the outdoor ambient temperature, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner;

[0008] Control the state of the electronic expansion valve according to the load rate and the bottom oil temperature, and control the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes an initial opening degree and an opening degree adjustment.

[0009] According to an embodiment of the present invention, the step of controlling the state of the electronic expansion valve according to the load rate and the bottom oil temperature specifically includes:

[0010] Adjust the opening degree of the electronic expansion valve to the initial start opening degree according to the load rate and the corresponding relationship of the predetermined initial opening degree;

[0011] Adjust the opening degree of the electronic expansion valve based on the temperature difference between two adjacent bottom oil temperatures every first period; wherein, the opening degree of the electronic expansion valve is greater than or equal to the minimum preset opening degree.

[0012] According to an embodiment of the present invention, the step of adjusting the opening degree of the electronic expansion valve based on the temperature difference between two adjacent bottom oil temperatures specifically includes:

[0013] When the temperature difference between the bottom oil temperature obtained this time and the bottom oil temperature obtained last time is greater than or equal to the preset temperature difference, control the opening degree of the electronic expansion valve to be at the initial start opening degree;

[0014] When the temperature difference between the bottom oil temperature obtained this time and the bottom oil temperature obtained last time is less than the preset temperature difference, control the opening degree of the electronic expansion valve to be reduced by a preset ratio.

[0015] According to an embodiment of the present invention, the step of controlling the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature and the suction temperature specifically includes:

[0016] When the outdoor ambient temperature is less than or equal to the low temperature threshold, control the solenoid valve to close;

[0017] When the outdoor ambient temperature is greater than the low temperature threshold, control the solenoid valve to close, and after the first preset time period, control the state of the solenoid valve according to the bottom oil temperature and the suction temperature every second period.

[0018] According to an embodiment of the present invention, after the start-up stage, there is also an operation stage. In the operation stage:

[0019] Obtain the operation mode of the multi-connected air conditioner, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner;

[0020] Control the state of the solenoid valve according to the operation mode, the bottom oil temperature and the suction temperature, and control the state of the electronic expansion valve according to the operation mode, the load rate, the bottom oil temperature and the suction temperature.

[0021] According to an embodiment of the present invention, the step of controlling the state of the solenoid valve according to the operation mode, the bottom oil temperature and the suction temperature specifically includes:

[0022] Determine a temperature threshold according to the operating mode and a predetermined threshold temperature relationship;

[0023] When the temperature difference between the bottom oil temperature and the suction temperature is greater than the temperature threshold, control the solenoid valve to open;

[0024] When the temperature difference between the bottom oil temperature and the suction temperature is less than or equal to the temperature threshold and the duration exceeds a second preset duration, control the solenoid valve to close.

[0025] According to an embodiment of the present invention, the step of controlling the state of the electronic expansion valve according to the operating mode, the load rate, the bottom oil temperature, and the suction temperature specifically includes:

[0026] Determine an initial operating opening degree correspondence according to the operating mode, and adjust the opening degree of the electronic expansion valve to the initial operating opening degree according to the load rate and the initial operating opening degree correspondence;

[0027] Adjust the opening degree of the electronic expansion valve every third cycle according to the operating mode, the bottom oil temperature, and the suction temperature.

[0028] According to an embodiment of the present invention, the step of adjusting the opening degree of the electronic expansion valve according to the operating mode, the bottom oil temperature, and the suction temperature specifically includes:

[0029] Determine a plurality of temperature intervals according to the operating mode, and adjust the opening degree of the electronic expansion valve according to the correspondence between the temperature difference between the bottom oil temperature and the suction temperature and the plurality of temperature intervals.

[0030] According to the oil return control device of a multi-connected air conditioner provided by the second aspect embodiment of the present invention, it includes:

[0031] An acquisition module for acquiring the outdoor ambient temperature, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner;

[0032] A control module for controlling the state of the electronic expansion valve according to the load rate and the bottom oil temperature, and controlling the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature, and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes an initial opening degree and an opening degree adjustment.

[0033] According to the multi-connected air conditioner provided by the third aspect embodiment of the present invention, it includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements the steps of the oil return control method of the multi-connected air conditioner provided by the first aspect embodiment of the present invention.

[0034] One or more of the above technical solutions in the present invention have at least one of the following technical effects:

[0035] According to the oil return control method of the multi-connected air conditioner provided by the embodiment of the present invention, the bottom of the gas-liquid separator is connected to the suction port of the compressor through a drain pipe. A valve group composed of a solenoid valve and an electronic expansion valve in parallel is provided on the drain pipe. A first temperature sensor is provided upstream of the valve group, and a second temperature sensor is provided downstream of the valve group. The control method includes a startup stage. In the startup stage: obtain the outdoor ambient temperature, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner; control the state of the electronic expansion valve according to the load rate and the bottom oil temperature, and control the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature, and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes an initial opening degree and an opening degree adjustment. When the lubricating oil deposits in the gas-liquid separator, by controlling the states of the electronic expansion valve and the solenoid valve, the lubricating oil at the bottom of the gas-liquid separator can be returned to the compressor to avoid the lack of oil fault of the compressor. Description of the Drawings

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following will briefly introduce the drawings required for use in the description of the embodiments or related technologies. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0037] Figure 1 Schematic structural diagram of the multi-connected air conditioner provided by the embodiment of the present invention;

[0038] Figure 2 Flow chart of the oil return control method of the multi-connected air conditioner provided by the embodiment of the present invention;

[0039] Figure 3 Schematic structural diagram of the oil return control device of the multi-connected air conditioner provided by the embodiment of the present invention;

[0040] Figure 4 Schematic structural diagram of the electronic device of the multi-connected air conditioner provided by the embodiment of the present invention.

[0041] Reference Signs:

[0042] 10. Compressor; 11. Outdoor heat exchanger; 12. Indoor heat exchanger; 13. Four-way valve; 14. Gas-liquid separator; 20. Drain pipe; 21. Solenoid valve; 22. Electronic expansion valve; 23. First temperature sensor; 24. Second temperature sensor;

[0043] 301. Acquisition module; 302. Control module. Detailed implementation manner

[0044] To make the objectives, technical solutions, and advantages of the invention clearer, the technical solutions in the invention will be clearly described below with reference to the accompanying drawings in the invention. Obviously, the described embodiments are some but not all of the embodiments of the invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the invention without creative efforts shall fall within the scope of protection of the invention.

[0045] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the embodiments of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0046] In the description of the embodiments of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0047] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over", and "on" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "below", "beneath", and "under" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0048] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0049] The multi-connected air conditioner involved in the present invention includes multiple indoor units and / or multiple outdoor units. When multiple indoor units and / or multiple outdoor units work simultaneously, the refrigerant demand is relatively large. During the startup phase, the operation phase under harsh working conditions, and when some indoor units or some outdoor units are working, the refrigerant demand decreases, and a large amount of lubricating oil deposits at the bottom of the gas-liquid separator, thereby resulting in a lack of lubricating oil in the compressor. Please refer to Figure 1 , in the embodiment of the present invention, the connection relationship of the refrigerant circulation circuit is schematically shown by one indoor heat exchanger and one outdoor heat exchanger. The multi-connected air conditioner includes a compressor 10, an outdoor heat exchanger 11, an indoor heat exchanger 12, a throttle valve, a gas-liquid separator 14, and a four-way valve 13. The compressor 10, the outdoor heat exchanger 11, the indoor heat exchanger 12, and the throttle valve are connected through refrigerant pipelines to form a refrigerant circulation circuit. The four-way valve 13 is arranged on the refrigerant circulation circuit and is used to adjust the flow direction of the refrigerant, thereby adjusting the operation mode of the multi-connected air conditioner. A gas-liquid separator 14 is arranged upstream of the suction port of the compressor 10. The gas-liquid separator 14 includes an air inlet and an air outlet. The air inlet is communicated with the return pipe of the refrigerant circulation circuit, and the air outlet is communicated with the suction port of the compressor 10 through a refrigerant pipeline. If there is liquid refrigerant in the air pipe or there is more liquid refrigerant in the refrigerant circulation circuit, the liquid refrigerant will be stored in the gas-liquid separator 14 to avoid entering the suction port of the compressor 10.

[0050] Please refer to Figure 1, a drain pipe 20 is provided at the bottom of the gas-liquid separator 14, and the other end of the drain pipe 20 communicates with the suction port of the compressor 10. A valve group is provided on the drain pipe 20. The valve group includes a solenoid valve 21 and an electronic expansion valve 22 connected in parallel. The lubricating oil in the gas-liquid separator 14 can flow into the suction port of the compressor 10 along the solenoid valve 21 or along the electronic expansion valve 22. A first temperature sensor 23 and a second temperature sensor 24 are also provided on the drain pipe 20. The first temperature sensor 23 is located upstream of the valve group and is used to detect the oil temperature at the bottom of the gas-liquid separator 14 (when there is no lubricating oil, the refrigerant temperature is detected). The second temperature sensor 24 is located downstream of the valve group and is used to detect the suction temperature of the compressor 10. The refrigerant pipeline at the outlet of the gas-liquid separator 14 communicates with the pipeline between the valve group and the first temperature sensor 23. When there is lubricating oil in the gas-liquid separator 14, by controlling the states of the solenoid valve 21 and the electronic expansion valve 22, the lubricating oil can be made to enter the suction port of the compressor 10 along the drain pipe 20. At the same time, when controlling the lubricating oil to enter the compressor 10 along the drain pipe 20, the refrigerant amount in the gas-liquid separator 14 also needs to be considered. When the multi-connected air conditioner is in a harsh working condition and a low refrigerant utilization rate stage, there is a large amount of refrigerant in the gas-liquid separator 14. At this time, if lubricating oil is introduced into the compressor 10 through the drain pipe 20, the liquid refrigerant may enter the suction port of the compressor 10 simultaneously with the lubricating oil. Therefore, on the one hand, the embodiment of the present invention needs to solve the problem of timely introducing lubricating oil into the compressor, and on the other hand, it needs to prevent the liquid refrigerant from flowing into the compressor 10 simultaneously with the lubricating oil.

[0051] In the embodiment of the present invention, according to the outdoor ambient temperature and the operation mode of the multi-connected air conditioner, etc., it can be determined whether it is currently in a harsh working condition, such as a low-temperature refrigeration working condition; according to the oil temperature at the bottom of the gas-liquid separator and the suction temperature of the compressor, it can be determined whether there is lubricating oil that needs to be discharged in the gas-liquid separator. When there is lubricating oil, the temperature change of the oil temperature at the bottom within adjacent detection cycles is small, while the temperature change of the suction temperature within adjacent detection cycles is large. Therefore, when the oil temperature at the bottom does not change and the suction temperature changes greatly, it indicates that there is lubricating oil that needs to be discharged at the bottom of the gas-liquid separator; or the small change of the oil temperature at the bottom within adjacent cycles also proves that there is lubricating oil that needs to be discharged at the bottom of the gas-liquid separator.

[0052] According to the oil return control method of the multi-connected air conditioner provided by the first aspect embodiment of the present invention, please refer to Figure 2 , the oil return control method of the multi-connected air conditioner includes a start-up stage. In the start-up stage:

[0053] S100. Obtain the ambient temperature, the oil temperature at the bottom of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner.

[0054] It can be understood that the outdoor ambient temperature can be obtained through a temperature sensor installed on the outdoor unit, or through an independent outdoor temperature sensor. The temperature sensor is electrically connected to the controller of the multi-connected air conditioner. During the startup phase, the multi-connected air conditioner first operates in the cooling mode, or executes the previously determined cooling mode during the startup phase. If the outdoor ambient temperature is low at this time, there is a situation of low-temperature cooling. At this time, the utilization rate of the refrigerant is low, which belongs to an extremely harsh working condition. Therefore, it is necessary to determine whether such an extreme working condition exists based on the outdoor ambient temperature. Secondly, the temperature difference between the bottom oil temperature of the gas-liquid separator and the suction temperature of the compressor can reflect whether there is lubricating oil that needs to be discharged inside the gas-liquid separator; thirdly, the change of the bottom oil temperature within adjacent cycles can also reflect whether there is lubricating oil that needs to be discharged inside the gas-liquid separator; thirdly, the load rate of the multi-connected air conditioner refers to the ratio of the capacity of the indoor units in the working state to the total capacity of the indoor units. For example, the load rates are 25%, 50%, 60%, 70%, 100%, etc. The lower the load rate of the multi-connected air conditioner, the lower the utilization rate of the refrigerant in the refrigerant circulation circuit, the more liquid refrigerant stored in the gas-liquid separator, and the more serious the deposition of lubricating oil in the gas-liquid separator.

[0055] S110. Control the state of the electronic expansion valve according to the load rate and the bottom oil temperature, and control the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes the initial opening degree and the opening degree adjustment.

[0056] In step S110, when controlling the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature and the suction temperature, when the multi-connected air conditioner is in an extreme low-temperature cooling working condition or there is a large amount of liquid refrigerant in the gas-liquid separator, control the solenoid valve to close. If the solenoid valve is opened at this time, a large amount of liquid refrigerant and lubricating oil will enter the suction port of the compressor together; in non-extreme low-temperature cooling working conditions, it is necessary to determine whether there is lubricating oil in the gas-liquid separator according to the bottom oil temperature and the suction temperature. If there is, it is necessary to control the solenoid valve to open, and if not, it is necessary to control the solenoid valve to close. During the startup phase, if the load rate is low, the amount of liquid refrigerant in the gas-liquid separator is large, and the initial startup opening degree of the electronic expansion valve should not be opened too large to avoid liquid refrigerant and lubricating oil from entering the suction port of the compressor along the drain pipe together. Subsequently, the situation of lubricating oil in the gas-liquid separator can be determined based on the bottom oil temperature, and then the opening degree of the electronic expansion valve can be further adjusted to timely introduce the lubricating oil into the compressor to avoid the phenomenon of lubricating oil shortage in the compressor.

[0057] When lubricating oil is deposited in the gas-liquid separator, by controlling the states of the electronic expansion valve and the solenoid valve, part of the lubricating oil at the bottom of the gas-liquid separator can be returned to the compressor to avoid oil shortage failure of the compressor.

[0058] In some embodiments, the step of controlling the state of the electronic expansion valve according to the load rate and the bottom oil temperature specifically includes:

[0059] S111. Adjust the opening of the electronic expansion valve to the initial startup opening according to the load rate and the corresponding relationship between the predetermined initial opening.

[0060] It can be understood that in the startup stage, if the load rate of the multi-connected air conditioner is low, the utilization rate of the refrigerant in the refrigerant circulation circuit is low, there is a large amount of liquid refrigerant in the gas-liquid separator, and a large amount of lubricating oil is deposited at the bottom of the gas-liquid separator. Therefore, the initial startup opening of the electronic expansion valve can be determined according to the corresponding relationship between the load rate and the initial opening, and the initial startup opening is positively correlated with the load rate. When the load rate is low, reducing the initial startup opening of the electronic expansion valve can slowly drain the lubricating oil at the bottom of the gas-liquid separator into the compressor, avoid the synchronous entry of liquid refrigerant into the compressor, and reduce the occurrence of liquid hammer phenomenon.

[0061] S112. Adjust the opening of the electronic expansion valve based on the temperature difference between the bottom oil temperatures of two adjacent times every first period; wherein, the opening of the electronic expansion valve is greater than or equal to the minimum preset opening.

[0062] In step S112, when controlling the electronic expansion valve to be at the initial startup opening according to the load rate, it can take into account supplying oil to the compressor and avoiding liquid refrigerant from entering the compressor. With the operation of the compressor and the discharge of the lubricating oil in the gas-liquid separator, the situation of the lubricating oil in the gas-liquid separator is also changing. Therefore, the opening of the electronic expansion valve can be adjusted every first period, such as 10 seconds. If there is still a large amount of lubricating oil in the gas-liquid separator and the temperature of the lubricating oil changes little during adjacent adjustment periods, that is, the temperature difference value between the bottom oil temperatures of two adjacent times is small or the change is small, it means that there is still lubricating oil to be discharged in the gas-liquid separator, and the opening of the electronic expansion valve can be controlled to increase or remain unchanged; if the temperature difference between the bottom oil temperatures of two adjacent times is large, it means that the lubricating oil has been emptied and the bottom oil temperature detected last time is already the temperature of the gaseous refrigerant. At this time, the opening of the electronic expansion valve can be reduced. It should be noted that the opening of the electronic expansion valve is greater than or equal to the minimum preset opening, and the minimum preset opening can maintain the return of the lubricating oil during the normal operation stage.

[0063] In some embodiments, the step of adjusting the opening of the electronic expansion valve based on the temperature difference between the bottom oil temperatures of two adjacent times specifically includes:

[0064] S1121. When the temperature difference between the bottom oil temperature obtained this time and the bottom oil temperature obtained last time adjacent to it is greater than or equal to the preset temperature difference, control the opening of the electronic expansion valve to be at the initial startup opening.

[0065] It can be understood that if the preset temperature difference is set to 0 °C, when the temperature difference between the bottom oil temperature obtained this time and the bottom oil temperature obtained in the previous adjacent acquisition is greater than or equal to 0 °C, the bottom of the gas-liquid separator has not yet contacted the gaseous refrigerant, and there is still a large amount of lubricating oil. At this time, it is necessary to keep the opening of the electronic expansion valve at the initial startup opening to facilitate the timely introduction of the lubricating oil in the gas-liquid separator into the compressor and avoid oil shortage in the compressor.

[0066] S1122. When the temperature difference between the bottom oil temperature obtained this time and the bottom oil temperature obtained in the previous adjacent acquisition is less than the preset temperature difference, control the opening of the electronic expansion valve to decrease by a preset ratio.

[0067] It can be understood that when the temperature difference between the bottom oil temperature obtained this time and the bottom oil temperature obtained in the previous adjacent acquisition is less than 0 °C, it means that there was lubricating oil at the bottom of the gas-liquid separator during the previous adjacent detection, and the bottom of the gas-liquid separator is already gaseous refrigerant during this detection, and the deposited lubricating oil has been discharged into the compressor. Therefore, the opening of the electronic expansion valve can be controlled to decrease by a preset ratio. For example, the valve opening is decreased by 20% pls based on the current opening, and it is adjusted once every 10 seconds. The minimum preset opening of the electronic expansion valve is 10% of the rated opening.

[0068] In some embodiments, the step of controlling the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature, and the suction temperature specifically includes:

[0069] S113. When the outdoor ambient temperature is less than or equal to the low temperature threshold, control the solenoid valve to close.

[0070] It can be understood that the low temperature threshold is used to define whether the multi-split air conditioner is in a low temperature environment. For example, the low temperature threshold is 15 °C. If the multi-split air conditioner is in an extremely harsh working condition of low temperature refrigeration, there is a large amount of refrigerant in the gas-liquid separator. Control the solenoid valve to close to avoid liquid refrigerant and lubricating oil from entering the suction port of the compressor together and avoid liquid hammer phenomenon.

[0071] S114. When the outdoor ambient temperature is greater than the low temperature threshold, control the solenoid valve to close, and after the first preset duration, control the state of the solenoid valve every second period according to the bottom oil temperature and the suction temperature.

[0072] In step S112, when the outdoor ambient temperature is greater than the low temperature threshold, the multi-split air conditioner is not in the low temperature refrigeration working condition, but at this time the multi-split air conditioner is still in the startup stage, the refrigerant utilization rate is low, and there is still a large amount of lubricating oil and liquid refrigerant in the gas-liquid separator. The solenoid valve needs to be in the closed state. After the multi-split air conditioner runs for the first preset duration, for example, 3 minutes later, every second period, for example, 30 seconds, determine the liquid refrigerant and lubricating oil conditions in the gas-liquid separator based on the bottom oil temperature and the suction temperature, and then control the on-off state of the solenoid valve.

[0073] For example, let the bottom oil temperature be Temp1 and the suction temperature be Temp2, and a determination is made every 30 s:

[0074] When Temp1 - Temp2 ≥ 0°C, the solenoid valve opens.

[0075] When Temp1 - Temp2 < 0°C, the solenoid valve closes.

[0076] According to an embodiment of the present invention, after the startup stage, there is also an operation stage, and in the operation stage:

[0077] S120. Obtain the operation mode of the multi-connected air conditioner, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner.

[0078] It can be understood that in the operation stage, the multi-connected air conditioner includes at least a refrigeration mode and a heating mode. In the refrigeration mode and the heating mode, the temperature differences used to determine whether there is lubricating oil or liquid refrigerant in the gas-liquid separator are different, and the initial opening degrees of the electronic expansion valves are also different. In the embodiments of the present invention, for different operation modes of the multi-connected air conditioner, based on the refrigerant situation in the gas-liquid separator, the states of the solenoid valve and the electronic expansion valve are respectively controlled to enable the lubricating oil to enter the compressor in time and prevent the liquid refrigerant from entering the suction port of the compressor.

[0079] S130. Control the state of the solenoid valve according to the operation mode, the bottom oil temperature, and the suction temperature, and control the state of the electronic expansion valve according to the operation mode, the load rate, the bottom oil temperature, and the suction temperature.

[0080] In step S130, the operation mode affects the determination of the lubricating oil situation and the liquid refrigerant situation in the gas-liquid separator, and there are differences in parameter selection between the refrigeration mode and the heating mode. In the operation stage, if the bottom oil temperature is greater than the suction temperature, or the temperature difference between the bottom oil temperature and the suction temperature is large, it indicates that there is still lubricating oil at the bottom of the gas-liquid separator, and the solenoid valve can be in the open state; if the bottom oil temperature is less than the suction temperature, or the temperature difference between the bottom oil temperature and the suction temperature is less than or equal to a certain value, the bottom oil temperature detects the temperature of the gaseous refrigerant, and at this time, the solenoid valve can be controlled to close.

[0081] In some embodiments, the step of controlling the state of the solenoid valve according to the operation mode, the bottom oil temperature, and the suction temperature specifically includes:

[0082] S131. Determine the temperature threshold according to the operation mode and the predetermined threshold temperature relationship.

[0083] S132. When the temperature difference between the bottom oil temperature and the suction temperature is greater than the temperature threshold, control the solenoid valve to open.

[0084] S133. When the temperature difference between the bottom oil temperature and the suction temperature is less than or equal to the temperature threshold and the duration exceeds the second preset duration, control the solenoid valve to close.

[0085] The following is an example:

[0086] When the operating mode is the refrigeration mode and the temperature threshold is 0 °C, then:

[0087] (1) When Temp1 - Temp2 > 0 °C, control the solenoid valve to open;

[0088] (2) When Temp1 - Temp2 ≤ 0 °C and the duration exceeds 3 min, control the solenoid valve to close.

[0089] When the operating mode is the heating mode and the temperature threshold is -2 °C, then:

[0090] (1) When Temp1 - Temp2 > -2 °C, control the solenoid valve to open;

[0091] (2) When Temp1 - Temp2 ≤ -2 °C and the duration exceeds 3 min, control the solenoid valve to close.

[0092] In some embodiments, the steps of controlling the state of the electronic expansion valve according to the operating mode, load rate, bottom oil temperature, and suction temperature specifically include:

[0093] S134. Determine the initial operating opening correspondence according to the operating mode, and adjust the opening of the electronic expansion valve to the initial operating opening according to the load rate and the initial operating opening correspondence.

[0094] S135. Adjust the opening of the electronic expansion valve every third cycle according to the operating mode, bottom oil temperature, and suction temperature.

[0095] It can be understood that the load rate is positively correlated with the refrigerant utilization rate in the refrigerant circulation circuit. When the load rate is low, the refrigerant utilization rate is low. At this time, there is a large amount of liquid refrigerant in the gas-liquid separator, and the opening of the electronic expansion valve needs to be adjusted to a smaller initial operating opening to prevent the liquid refrigerant and lubricating oil from entering the compressor along the drain pipe together. In different operating modes, the initial operating opening correspondence is different, that is, in different operating modes, the correspondence between the load rate and the initial operating opening is different. After the electronic expansion valve is adjusted to the initial operating opening, the lubricating oil situation in the gas-liquid separator is further determined according to the bottom oil temperature and the suction temperature, and then the opening of the electronic expansion valve is adjusted.

[0096] The following is an example:

[0097] In the refrigeration mode: when the load rate is lower than 25%, the initial opening degree of the electronic expansion valve is 40% pls; when the load rate is lower than 50%, the initial opening degree of the electronic expansion valve is 50% pls; when the load rate is higher than 50%, the initial opening degree of the electronic expansion valve is 70% pls.

[0098] In the heating mode: when the load rate is lower than 25%, the initial opening degree of the electronic expansion valve is 30% pls; when the load rate is lower than 50%, the initial opening degree of the electronic expansion valve is 40% pls; when the load rate is higher than 50%, the initial opening degree of the electronic expansion valve is 50% pls.

[0099] In some embodiments, the step of adjusting the opening degree of the electronic expansion valve according to the operating mode, the bottom oil temperature, and the suction temperature specifically includes:

[0100] S1351. Determine multiple temperature ranges according to the operating mode, and adjust the opening degree of the electronic expansion valve according to the corresponding relationship between the temperature difference between the bottom oil temperature and the suction temperature and the multiple temperature ranges.

[0101] In step S1351, the temperature difference between the bottom oil temperature and the suction temperature can reflect the lubricating oil condition at the bottom of the gas-liquid separator. For example, when the temperature difference between the bottom oil temperature and the suction temperature is large, it proves that the temperature of the gaseous refrigerant at the suction port is low, and the stock of the lubricating oil at the bottom of the gas-liquid separator is still large. The refrigerant in the gas-liquid separator has been added to the refrigerant cycle in a gaseous form, and the opening degree of the electronic expansion valve can be increased to accelerate the entry of the lubricating oil into the compressor. At this time, the risk of refrigerant liquid slugging is small. The following is an example:

[0102] In the refrigeration mode, let the bottom oil temperature be Temp1 and the suction temperature be Temp2, and make a determination every 30 s:

[0103] (1) When Temp1 - Temp2 > 40°C, the valve opening degree of the electronic expansion valve is increased by 12% on the original basis;

[0104] (2) When 20°C < Temp1 - Temp2 ≤ 40°C, the valve opening degree of the electronic expansion valve is increased by 10% on the original basis;

[0105] (3) When 5°C < Temp1 - Temp2 ≤ 20°C, the valve opening degree of the electronic expansion valve is increased by 6% on the original basis;

[0106] (4) When -2°C < Temp1 - Temp2 ≤ 5°C, the valve opening degree of the electronic expansion valve remains unchanged;

[0107] (5) When Temp1 - Temp2 ≤ -2°C, the valve opening degree of the electronic expansion valve is decreased by 5% on the original basis.

[0108] In the heating mode, let the bottom oil temperature be Temp1 and the suction temperature be Temp2, and a determination is made every 30 s:

[0109] (1) When Temp1 - Temp2 > 20°C, the valve opening of the electronic expansion valve is increased by 8% on the original basis;

[0110] (2) When 5°C < Temp1 - Temp2 ≤ 20°C, the valve opening of the electronic expansion valve is increased by 3% on the original basis;

[0111] (3) When -2°C < Temp1 - Temp2 ≤ 5°C, the valve opening of the electronic expansion valve remains unchanged;

[0112] (4) When Temp1 - Temp2 ≤ -2°C, the valve opening of the electronic expansion valve is reduced by 5% on the original basis.

[0113] For the oil return control device of the multi-connected air conditioner according to the second aspect embodiment of the present invention, please refer to Figure 3 , including:

[0114] An acquisition module 301, configured to acquire the outdoor ambient temperature, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner;

[0115] A control module 302, configured to control the state of the electronic expansion valve according to the load rate and the bottom oil temperature, and control the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature, and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes the initial opening and the opening adjustment.

[0116] It should be noted that the above steps S100 to S130, as well as other steps, are only for convenience of expression and do not constitute a timing limitation on the steps in the oil return control method of the multi-connected air conditioner. And some contents are described in detail in the oil return control method of the multi-connected air conditioner provided in the first aspect embodiment, and all the contents in the oil return control method of the multi-connected air conditioner are also applicable to the oil return control device of the multi-connected air conditioner provided in the second aspect embodiment. Therefore, in order to avoid repetition, it is not described in detail in the oil return control device of the multi-connected air conditioner provided in the second aspect embodiment. Similarly, the contents in the above two aspect embodiments can be used to explain the contents of all subsequent aspect embodiments. Therefore, the repeated contents are not described in the subsequent embodiments. For the oil return control device of the multi-connected air conditioner according to the embodiment of the present invention, its technical effects correspond to those of the above-mentioned oil return control method of the multi-connected air conditioner, and will not be elaborated here.

[0117] The multi-connected air conditioner according to the embodiment of the third aspect of the present invention includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements the steps of the oil return control method of the multi-connected air conditioner according to the embodiment of the first aspect of the present invention.

[0118] Figure 4 The schematic diagram of the physical structure of an electronic device of a multi-connected air conditioner is illustrated. The electronic device may include: a processor 810, a communication interface 820, a memory 830, and a communication bus 840. Among them, the processor 810, the communication interface 820, and the memory 830 complete mutual communication through the communication bus 840. The processor 810 can call the logical instructions in the memory 830 to execute the oil return control method of the multi-connected air conditioner. The method includes: obtaining the outdoor ambient temperature, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner; controlling the state of the electronic expansion valve according to the load rate and the bottom oil temperature, and controlling the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature, and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes the initial opening and the opening adjustment.

[0119] In addition, when the above logical instructions in the memory 830 are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs that can store program codes.

[0120] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative effort.

[0121] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the essence of the above technical solution, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for causing a computer device (which can be a personal computer, server, or network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0122] The above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An oil return control method for a multi-connected air conditioner, characterized in that, the bottom of the gas-liquid separator is connected to the suction port of the compressor through a drain pipe, and the drain pipe is provided with a valve group composed of a solenoid valve and an electronic expansion valve in parallel. A first temperature sensor is provided upstream of the valve group, and a second temperature sensor is provided downstream of the valve group. The control method includes a startup stage, and in the startup stage: Obtain the outdoor ambient temperature, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner; Control the state of the electronic expansion valve according to the load rate and the bottom oil temperature, and control the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature, and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes an initial opening degree and an opening degree adjustment.

2. The oil return control method for a multi-connected air conditioner according to claim 1, characterized in that, the step of controlling the state of the electronic expansion valve according to the load rate and the bottom oil temperature specifically includes: Adjust the opening degree of the electronic expansion valve to the initial startup opening degree according to the load rate and the predetermined initial opening degree correspondence; Adjust the opening degree of the electronic expansion valve based on the temperature difference between two adjacent bottom oil temperatures every first period; wherein, the opening degree of the electronic expansion valve is greater than or equal to the minimum preset opening degree.

3. The oil return control method for a multi-connected air conditioner according to claim 2, characterized in that, the step of adjusting the opening degree of the electronic expansion valve based on the temperature difference between two adjacent bottom oil temperatures specifically includes: When the temperature difference between the bottom oil temperature obtained this time and the bottom oil temperature obtained last time is greater than or equal to the preset temperature difference, control the opening degree of the electronic expansion valve to be at the initial startup opening degree; When the temperature difference between the bottom oil temperature obtained this time and the bottom oil temperature obtained last time is less than the preset temperature difference, control the opening degree of the electronic expansion valve to be reduced by a preset ratio.

4. The oil return control method for a multi-connected air conditioner according to any one of claims 1 to 3, characterized in that, the step of controlling the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature, and the suction temperature specifically includes: When the outdoor ambient temperature is less than or equal to the low temperature threshold, control the solenoid valve to close; When the outdoor ambient temperature is greater than the low temperature threshold, control the solenoid valve to close, and after the first preset duration, control the state of the solenoid valve according to the bottom oil temperature and the suction temperature every second period.

5. The oil return control method for a multi-connected air conditioner according to claim 4, characterized in that, a running stage is further included after the startup stage, and in the running stage: Obtain the running mode of the multi-connected air conditioner, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor, and the load rate of the multi-connected air conditioner; Control the state of the solenoid valve according to the running mode, the bottom oil temperature, and the suction temperature, and control the state of the electronic expansion valve according to the running mode, the load rate, the bottom oil temperature, and the suction temperature.

6. The oil return control method for a multi-connected air conditioner according to claim 5, It is characterized in that The step of controlling the state of the solenoid valve according to the operation mode, the bottom oil temperature and the suction temperature specifically includes: Determine the temperature threshold according to the operation mode and the predetermined threshold temperature relationship; When the temperature difference between the bottom oil temperature and the suction temperature is greater than the temperature threshold, control the solenoid valve to open; When the temperature difference between the bottom oil temperature and the suction temperature is less than or equal to the temperature threshold and the duration exceeds the second preset duration, control the solenoid valve to close.

7. The oil return control method for a multi-connected air conditioner according to claim 5, It is characterized in that The step of controlling the state of the electronic expansion valve according to the operation mode, the load rate, the bottom oil temperature and the suction temperature specifically includes: Determine the initial operation opening degree correspondence according to the operation mode, and adjust the opening degree of the electronic expansion valve to the initial operation opening degree according to the load rate and the initial operation opening degree correspondence; Adjust the opening degree of the electronic expansion valve every third period according to the operation mode, the bottom oil temperature and the suction temperature.

8. The oil return control method for a multi-connected air conditioner according to claim 7, It is characterized in that The step of adjusting the opening degree of the electronic expansion valve according to the operation mode, the bottom oil temperature and the suction temperature specifically includes: Determine multiple temperature intervals according to the operation mode, and adjust the opening degree of the electronic expansion valve according to the correspondence between the temperature difference between the bottom oil temperature and the suction temperature and the multiple temperature intervals.

9. An oil return control device for a multi-connected air conditioner, It is characterized in that It includes: An acquisition module for acquiring the outdoor ambient temperature, the bottom oil temperature of the gas-liquid separator, the suction temperature of the compressor and the load rate of the multi-connected air conditioner; A control module for controlling the state of the electronic expansion valve according to the load rate and the bottom oil temperature, and controlling the state of the solenoid valve according to the outdoor ambient temperature, the bottom oil temperature and the suction temperature; wherein, the state of the solenoid valve includes open and closed, and the state of the electronic expansion valve includes the initial opening degree and the opening degree adjustment.

10. A multi-connected air conditioner, including a memory, a processor and a computer program stored on the memory and executable on the processor, It is characterized in that When the processor executes the program, the steps of the oil return control method for the multi-connected air conditioner according to any one of claims 1 to 8 are implemented.

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