A method for improving oil return of a compressor, an oil return system and a compressor

Abstract

The application provides a method for improving compressor oil return, an oil return system and a compressor. The method for improving compressor oil return is realized by using an oil return system in the compressor. The oil return system comprises a closed oil return unit connected between an oil separator and the compressor. The method comprises the following steps: obtaining a compressor operating state; calculating the capacity requirement q of all indoor units and the maximum refrigerating capacity Q under the current environment; determining whether high-frequency oil return conditions or low-frequency oil return conditions are met based on the obtained compressor operating state and the size relationship between q / Q and a preset ratio; and when the high-frequency oil return conditions or the low-frequency oil return conditions are met, controlling the opening of the closed oil return unit to perform high-frequency or low-frequency oil return processing. The application has a double-circuit oil return system, and timely oil return is realized through logical judgment of system parameters, so that long-term operation of the unit in an oil shortage state is avoided, the cylinder is not worn, and the operation reliability of the compressor is improved.

Description

Technical Field

[0001] This invention relates to the field of compressor technology, and in particular to a method, oil return system and compressor for improving compressor oil return. Background Technology

[0002] like Figure 1 As shown, in the field of air conditioning technology, the mixture of refrigerant and oil from compressor 1 enters oil separator 2, where the oil is separated, and the refrigerant enters the outdoor heat exchanger in an oil-free state. The separated oil is returned to compressor 1 through capillary tube 4. In existing air conditioners, capillary tube 4 is a single-return oil line. Because the length of capillary tube 4 is fixed, the amount of oil returned by compressor 1 is constant regardless of whether compressor 1 operates at low or high frequencies. This can easily lead to difficulty in oil return during low-frequency operation and excessive oil discharge during high-frequency operation, resulting in oil shortage.

[0003] The applicant has discovered that the prior art has at least the following technical problems: the fixed oil return volume of the single oil return line in the prior art air conditioner is prone to causing oil shortage in the compressor, and no effective solution has been proposed yet. Summary of the Invention

[0004] The purpose of this invention is to provide a method, system and compressor for improving oil return in a compressor, so as to solve the technical problem that the amount of oil returned by the compressor cannot be adjusted according to high and low frequency operation, which easily leads to difficulty in oil return or oil shortage.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for improving oil return in a compressor, which utilizes an oil return system in the compressor. The oil return system includes a closed-loop oil return unit connected between an oil separator and the compressor. The method includes the following steps:

[0007] Obtain the compressor's operating status;

[0008] Calculate the total capacity requirement q of all indoor units and the maximum cooling capacity Q under the current environment;

[0009] Based on the obtained compressor operating status, and combined with the relationship between q / Q and the preset ratio, it is determined whether the high-frequency oil return condition or the low-frequency oil return condition is met.

[0010] When the conditions for high-frequency or low-frequency oil return are met, the closed-loop oil return unit is opened to perform high-frequency or low-frequency oil return processing.

[0011] The present invention provides a method for improving compressor oil return by using logical judgment based on system parameters to ensure timely oil return, thus preventing the unit from operating for extended periods when oil is insufficient, which would cause wear on the cylinder. The new structure and control method contribute to improving the reliability of compressor operation.

[0012] As a further improvement of the present invention, the capacity requirement q of all indoor units is calculated according to the following formula:

[0013] q = ∑cmt0; where: t0 = t 设定 -t 目标 c is the specific heat capacity of the corresponding refrigerant, m is the mass of refrigerant passing through a single radiator, cmt0 is the capacity requirement of a single indoor unit, and q is the sum of the capacity requirements of all indoor units.

[0014] As a further improvement of the present invention, the maximum cooling capacity Q under the current environment is calculated according to the following formula:

[0015] Q = kn(azt); where k is the compressor coefficient of performance, n is the number of compressors, a is the cooling capacity of a single compressor, z is the ambient temperature correction factor, and t is the ambient temperature.

[0016] As a further improvement of the present invention, the step of determining whether the high-frequency oil return condition or the low-frequency oil return condition is met based on the acquired compressor operating status and the relationship between q / Q and a preset ratio includes:

[0017] When the compressor is running at low frequency, compare whether q / Q is less than the preset ratio A;

[0018] When q / Q is less than the preset ratio A, it is determined that the low-frequency oil return condition is met.

[0019] When the compressor is running at high frequency, compare whether q / Q is greater than the preset ratio B;

[0020] When q / Q is greater than the preset ratio B, it is determined that the high-frequency oil return condition is met.

[0021] As a further improvement of the present invention, the control of the closed-loop oil return unit for high-frequency or low-frequency oil return processing includes:

[0022] When the low-frequency oil return condition is met, the closed-loop oil return unit is opened to perform low-frequency oil return.

[0023] After the first set time for low-frequency oil return is completed, the closed-loop oil return unit is shut down, and the unit enters normal logic operation.

[0024] After the second set time of normal logic operation, the current compressor operating frequency is obtained;

[0025] When the compressor operating frequency is less than or equal to the first set frequency, the closed-loop oil return unit is opened to perform low-frequency oil return again; after the first set time of low-frequency oil return is completed, the closed-loop oil return unit is closed and the unit enters normal logic operation.

[0026] When the compressor operating frequency is greater than the first set frequency, the comparison will return to determine whether q / Q is less than the preset ratio A.

[0027] As a further improvement of the present invention, the control of the closed-loop oil return unit for high-frequency or low-frequency oil return processing includes:

[0028] When the high-frequency oil return condition is met, the closed-loop oil return unit is opened to perform high-frequency oil return.

[0029] After the third set time for high-frequency oil return is completed, the closed-loop oil return unit is shut down, and the unit enters normal logic operation.

[0030] After the second set time of normal logic operation, the current compressor operating frequency is obtained;

[0031] When the compressor operating frequency is greater than or equal to the second set frequency, the closed-loop oil return unit is opened to perform high-frequency oil return again; after the high-frequency oil return is completed for the third set time, the closed-loop oil return unit is closed and the unit enters normal logic operation.

[0032] When the compressor operating frequency is less than the second set frequency, the comparison will return to determine whether q / Q is greater than the preset ratio B.

[0033] As a further improvement of the present invention, before obtaining the compressor operating status, the process further includes: waiting for the compressor to run for a fourth set time.

[0034] As a further improvement of the present invention, the preset ratio A is 20% and the preset ratio B is 80%.

[0035] As a further improvement of the present invention, the first set time is 45 minutes.

[0036] As a further improvement of the present invention, the second set time is 2 hours.

[0037] As a further improvement of the present invention, the first set frequency is 30Hz.

[0038] As a further improvement of the present invention, the second set frequency is 70Hz.

[0039] As a further improvement of the present invention, the third set time is 30 minutes.

[0040] An oil return system provided by the present invention is used to execute the method. The oil return system includes a closed oil return unit connected between an oil separator and a compressor.

[0041] As a further improvement of the present invention, the closed oil return unit includes a closed oil separator return pipe, a return pipe solenoid valve or an electronic expansion valve; one end of the closed oil separator return pipe is connected to the oil separator, and the other end is connected to the bottom oil sump of the compressor; the return pipe solenoid valve or the electronic expansion valve is installed on the closed oil separator return pipe; alternatively, the closed oil return unit includes a capillary line, one end of the capillary line is connected to the oil separator, and the other end is connected to the bottom oil sump of the compressor.

[0042] A compressor provided by the present invention includes the oil return system.

[0043] The compressor of the present invention has a dual-loop oil return system, which makes logical judgments through system parameters and returns oil in a timely manner, solving the problem of difficult oil return in the low-frequency state. When the frequency is high, the oil running amount is large, and it makes the refrigerant evaporation process more uniform, improving the utilization rate of the heat exchanger, and solving the technical problem that the fixed oil return amount of the single oil return pipeline in the air conditioner in the prior art easily causes the compressor to lack oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] [[ID=I4]]In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. 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. [[ID=I5]]

[0045] Figure 1 is a schematic structural diagram of the oil return system in a compressor in the prior art;

[0046] Figure 2 is a schematic structural diagram of the oil return system in the compressor of the present invention;

[0047] Figure 3 is a control flowchart of the method for improving the oil return of the compressor of the present invention;

[0048] Figure 4 is an oil return logic diagram during low-frequency operation in the method for improving the oil return of the compressor of the present invention;

[0049] Figure 5 is an oil return logic diagram during high-frequency operation in the method for improving the oil return of the compressor of the present invention.

[0050] In the figure, 1 is the compressor; 2 is the oil separator; 3 is the gas-liquid separator; 4 is the capillary line; 5 is the closed oil separator return pipe; 6 is the return pipe oil return valve. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0052] like Figure 3 As shown, the present invention provides a method for improving oil return in a compressor, which is achieved by utilizing an oil return system in the compressor. The oil return system includes a closed-loop oil return unit connected between an oil separator and the compressor. The method includes the following steps:

[0053] Step S1: Obtain the compressor operating status; the compressor operating status includes low-frequency status and high-frequency status;

[0054] Considering the possibility of fluctuations in the compressor's initial operating parameters, a fourth set time is included after the compressor is started, before obtaining the compressor's operating status.

[0055] In this embodiment, the fourth set time can be 60 minutes, that is, the compressor operating status is obtained after the compressor has been running for 60 minutes.

[0056] Step S2: Calculate the capacity requirement q of all indoor units and the maximum cooling capacity Q under the current environment; where:

[0057] The capacity requirement q for all indoor units is calculated using the following formula:

[0058] q = ∑cmt0; where: t0 = t 设定 -t 目标 c is the specific heat capacity of the corresponding refrigerant, m is the mass of refrigerant passing through a single radiator, cmt0 is the capacity requirement of a single indoor unit, and q is the sum of the capacity requirements of all indoor units.

[0059] The maximum cooling capacity Q under the current environment is calculated using the following formula:

[0060] Q = kn(azt); where k is the compressor coefficient of performance, n is the number of compressors, a is the cooling capacity of a single compressor, z is the ambient temperature correction factor, and t is the ambient temperature.

[0061] Step S3: Based on the obtained compressor operating status, and combined with the relationship between q / Q and the preset ratio, determine whether the high-frequency oil return condition or the low-frequency oil return condition is met.

[0062] Specifically, as an optional embodiment of the present invention:

[0063] 1. When the compressor is running at low frequency, compare whether q / Q is less than the preset ratio A; if q / Q is less than the preset ratio A, it is determined that the low frequency oil return condition is met.

[0064] 2. When the compressor is running at high frequency, compare whether q / Q is greater than the preset ratio B; if q / Q is greater than the preset ratio B, it is determined that the high-frequency oil return condition is met.

[0065] Step S4: When the high-frequency oil return condition or the low-frequency oil return condition is met, control the opening of the closed oil return unit to perform high-frequency or low-frequency oil return processing.

[0066] Furthermore, controlling the opening of the closed-loop oil return unit to perform low-frequency oil return processing includes:

[0067] When the low-frequency oil return condition is met, the closed-loop oil return unit is opened to perform low-frequency oil return.

[0068] After the first set time for low-frequency oil return is completed, the closed-loop oil return unit is shut down, and the unit enters normal logic operation; after the second set time for normal logic operation, the current compressor operating frequency is obtained;

[0069] When the compressor operating frequency is less than or equal to the first set frequency, the closed-loop oil return unit is opened to perform low-frequency oil return again; after the first set time of low-frequency oil return is completed, the closed-loop oil return unit is closed and the unit enters normal logic operation; then the above normal logic operation is repeated for a second set time to obtain the current compressor operating frequency and subsequent steps.

[0070] When the compressor operating frequency is greater than the first set frequency, the comparison returns to determine if q / Q is less than the preset ratio A. Based on the comparison result, the corresponding subsequent steps are executed.

[0071] Furthermore, controlling the opening of the closed-loop oil return unit to perform high-frequency oil return processing includes:

[0072] When the high-frequency oil return condition is met, the closed-loop oil return unit is opened to perform high-frequency oil return.

[0073] After the third set time for high-frequency oil return is completed, the closed-loop oil return unit is shut down, and the unit enters normal logic operation.

[0074] After the second set time of normal logic operation, the current compressor operating frequency is obtained;

[0075] When the compressor operating frequency is greater than or equal to the second set frequency, the closed-loop oil return unit is opened to perform high-frequency oil return again; after the high-frequency oil return is completed for the third set time, the closed-loop oil return unit is closed and the unit enters normal logic operation; then the above normal logic operation is repeated for the second set time to obtain the current compressor operating frequency and subsequent steps;

[0076] If the compressor operating frequency is less than the second set frequency, the system returns to compare whether q / Q is greater than the preset ratio B. Based on the comparison result, the corresponding subsequent steps are executed.

[0077] In this embodiment, the preset ratio A is 20%, the preset ratio B is 80%, the first preset time is 45 minutes, the second preset time is 2 hours, the first preset frequency is 30 Hz, the second preset frequency is 70 Hz, and the third preset time is 30 minutes.

[0078] It should be noted that the closed-loop oil return unit includes three embodiments: a closed-loop oil return pipe and an oil return pipe solenoid valve; a closed-loop oil return pipe and an electronic expansion valve; or a capillary circuit. The control process of the three embodiments is slightly different. When using an oil return pipe solenoid valve, since the oil return pipe solenoid valve only has an on / off function, there is only an on / off control process, that is, oil return and stopping oil return control. The electronic expansion valve can adjust the opening degree, that is, in addition to realizing oil return control, it can also control the amount of oil return. The capillary circuit has the characteristic of adjusting the oil return speed, and the length of the capillary circuit is fixed, so no other control steps are required.

[0079] The present invention provides a method for improving compressor oil return by using logical judgment based on system parameters to ensure timely oil return, thus preventing the unit from operating for extended periods when oil is insufficient, which would cause wear on the cylinder. The new structure and control method contribute to improving the reliability of compressor operation.

[0080] Example 1:

[0081] In this embodiment, the present invention proposes a novel oil return control method for the oil return system in a compressor. This method avoids the unit from running for a long time when there is a lack of oil, which would wear down the cylinder and help improve the reliability of compressor operation.

[0082] In refrigeration systems, most compressor oil return systems utilize open-type oil return units. This relies on the system's suction to carry lubricating oil back to the compressor oil sump, and then using differential pressure and oil pumps to deliver the lubricating oil to the compression chamber for lubrication. Because this method requires the oil to go through a cycle before entering the compression chamber, there is a delay, leading to oil shortage in the compressor. Therefore, the compressor structure is adjusted by adding a closed-type oil separator return pipe and a return pipe solenoid valve. The oil from the oil separator directly enters the compression chamber, achieving a large-volume oil pumping effect.

[0083] The specific control methods are as follows:

[0084] When the compressor is running at low frequency, after the refrigeration system is turned on, the normal start-up control logic of the unit is executed, and it runs stably for 60 minutes.

[0085] (1) Calculate the capacity requirement of all indoor units q (q=∑cmt0(t0=t 设定 -t 目标 c: specific heat capacity of the refrigerant, m: mass of refrigerant passing through a single radiator, summed after calculating the demand capacity of all indoor units;

[0086] (2) Calculate the maximum cooling capacity Q under the current environment (Calculate the maximum cooling capacity Q under the current environment = kn(azt), where k is the compressor cooling coefficient; n is the number of compressors; a is the cooling capacity of a single compressor; z is the ambient temperature correction coefficient; t is the ambient temperature).

[0087] (3) Determine whether q / Q is less than A;

[0088] (4) If the value is less than A, the return oil pipe solenoid valve, capillary tube, or electronic expansion valve will be opened to perform auxiliary return oil operation. If the value is greater than A, the unit's normal logic control operation will be executed. (The return oil pipe solenoid valve only has an on / off function; the capillary tube can be fixed in length and slowly adjusted without needing to execute all logic relationships; the electronic expansion valve can be adjusted according to the suction superheat. When the suction superheat is -5℃ to -2℃, the electronic expansion valve is opened at 70%; when it is -2℃ to 0℃, it is opened at 50%; when it is 0℃ to 5℃, it is opened at 30%; when it is >5℃, the electronic expansion valve is closed. The formula for calculating the suction superheat is: Suction superheat = Suction pipe temperature - Saturated steam temperature)

[0089] (5) After the return oil pipe solenoid valve has been running for 45 minutes, the return oil pipe solenoid valve is closed.

[0090] (6) The unit starts up with conventional logic control operation;

[0091] (7) After the unit has been running for 2 hours, determine the current operating frequency of the compressor;

[0092] (8) If the frequency is greater than 30Hz, the unit shall operate according to the normal logic control program.

[0093] (9) If it is less than 30Hz, the return oil solenoid valve will be opened and (5) will be executed.

[0094] It should be noted that A can be between 5% and 30%. When the capacity is low, that is, below the range A (5% to 30%), the compressor's oil return power is insufficient, and an auxiliary oil return section needs to be added. The closed-loop oil return system serves as one of the auxiliary oil return channels.

[0095] Example 2:

[0096] When the compressor is running at low frequency, after the refrigeration system is turned on, the normal start-up control logic of the unit is executed, and it runs stably for 60 minutes.

[0097] (1) Calculate the capacity requirement of all indoor units q (q = cmt0 (t0 = t) 设定 -t 目标 c: specific heat capacity of the corresponding refrigerant, m: mass of refrigerant passing through a single radiator;

[0098] (2) Calculate the maximum cooling capacity Q under the current environment (Calculate the maximum cooling capacity Q under the current environment = k(azt), where k is the compressor cooling coefficient; a is the cooling capacity of a single compressor; z is the ambient temperature correction coefficient; t is the ambient temperature).

[0099] (3) Determine whether q / Q is greater than B;

[0100] (4) If the value is greater than B, the return oil pipe solenoid valve, capillary tube, or electronic expansion valve will be opened to perform auxiliary return oil action. If the value is less than B, the unit's normal logic control operation will be executed (where the return oil pipe solenoid valve only has an on / off function; the capillary tube has a fixed length and is slowly adjusted, and does not need to execute all logic relationships; the electronic expansion valve can be adjusted according to the suction superheat. When the suction superheat is -5℃ to -2℃, the electronic expansion valve is opened at 70%; when it is -2℃ to 0℃, it is opened at 50%; when it is 0℃ to 5℃, it is opened at 30%; when it is >5℃, the electronic expansion valve is closed. The formula for calculating the suction superheat is: Suction superheat = Suction pipe temperature - Saturated steam temperature).

[0101] (5) After the return oil pipe solenoid valve has been running for 30 minutes, the return oil pipe solenoid valve is closed.

[0102] (6) The unit starts up with conventional logic control operation;

[0103] (7) After the unit has been running for 2 hours, determine the current operating frequency of the compressor;

[0104] (8) If the frequency is greater than 70Hz, the unit shall operate according to the normal logic control program.

[0105] (9) If it is less than 70Hz, the return oil solenoid valve will be opened and (5) will be executed.

[0106] It should be noted that B can be between 80% and 100%: when the capacity requirement is greater than B (80% to 100%), the compressor's oil return power is indeed sufficient, but the oil discharge rate is also high. Therefore, under high load, it will be necessary to open the auxiliary oil return circuit.

[0107] The present invention provides an oil return system for performing a method, the oil return system including a closed-loop oil return unit connected between an oil separator and a compressor.

[0108] As a further improvement of the present invention, the closed-loop oil return unit includes a closed-loop oil separator return pipe and a return pipe solenoid valve. ； One end of the closed-loop oil separator return pipe is connected to the oil separator, and the other end is connected to the oil sump at the bottom of the compressor; the return pipe solenoid valve is installed on the closed-loop oil separator return pipe.

[0109] As another improvement of the present invention, the closed-loop oil return unit includes a closed-loop oil return pipe and an electronic expansion valve; one end of the closed-loop oil return pipe is connected to the oil separator, and the other end is connected to the oil sump at the bottom of the compressor; the electronic expansion valve is installed on the closed-loop oil return pipe.

[0110] As a third improvement of the present invention, the closed-loop oil return unit includes a capillary tube, one end of which is connected to an oil separator and the other end of which is connected to an oil sump at the bottom of the compressor.

[0111] The present invention provides a compressor including the above-mentioned oil return system.

[0112] The compressor of this invention has a dual-loop oil return system. By making logical judgments based on system parameters, it can return oil in a timely manner, which solves the problem of difficult oil return at low frequency. At high frequency, the amount of oil lost is greater, and the refrigerant evaporation process is more uniform, improving the utilization rate of the heat exchanger. It also solves the technical problem in the prior art where the fixed amount of oil returned by the single oil return pipeline in the air conditioner easily leads to oil shortage in the compressor.

[0113] First, it should be noted that "inward" refers to the direction towards the center of the storage space, while "outward" refers to the direction away from the center of the storage space.

[0114] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the appendix. Figure 1 The orientations or positional relationships shown are for the purpose of facilitating and simplifying the description of the present invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

[0115] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0116] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0117] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0118] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0119] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for improving oil return in a compressor, characterized in that, The method utilizes an oil return system in the compressor, the oil return system including a closed-loop oil return unit connected between an oil separator and the compressor; the method includes the following steps: Obtain the compressor's operating status; Calculate the total capacity requirement q of all indoor units and the maximum cooling capacity Q under the current environment; Based on the obtained compressor operating status, and combined with the relationship between q / Q and the preset ratio, it is determined whether the high-frequency oil return condition or the low-frequency oil return condition is met. When the low-frequency oil return condition is met, the closed-loop oil return unit is opened to perform low-frequency oil return; after the first set time of low-frequency oil return is completed, the closed-loop oil return unit is closed, and the unit enters normal logic operation; after the second set time of normal logic operation, the current compressor operating frequency is obtained; when the compressor operating frequency is ≤ the first set frequency, the closed-loop oil return unit is opened to perform low-frequency oil return again; after the first set time of the second low-frequency oil return is completed, the closed-loop oil return unit is closed, and the unit enters normal logic operation; when the compressor operating frequency is > the first set frequency, the comparison is returned to see if q / Q is less than the preset ratio A; When the high-frequency oil return condition is met, the closed-loop oil return unit is opened to perform high-frequency oil return; after the third set time of high-frequency oil return is completed, the closed-loop oil return unit is closed, and the unit enters normal logic operation; after the second set time of normal logic operation, the current compressor operating frequency is obtained; when the compressor operating frequency is ≥ the second set frequency, the closed-loop oil return unit is opened to perform high-frequency oil return again; after the third set time of high-frequency oil return is completed, the closed-loop oil return unit is closed, and the unit enters normal logic operation; when the compressor operating frequency is < the second set frequency, the comparison q / Q is returned to see if it is greater than the preset ratio B.

2. The method according to claim 1, characterized in that, The capacity requirement q for all indoor units is calculated using the following formula: q = ∑cmt0; where: t0 = t 设定 -t 目标 c is the specific heat capacity of the corresponding refrigerant, m is the mass of refrigerant passing through a single radiator, cmt0 is the capacity requirement of a single indoor unit, and q is the sum of the capacity requirements of all indoor units.

3. The method according to claim 1, characterized in that, The maximum cooling capacity Q under the current environment is calculated using the following formula: Q = kn(azt); where k is the compressor coefficient of performance, n is the number of compressors, a is the cooling capacity of a single compressor, z is the ambient temperature correction factor, and t is the ambient temperature.

4. The method according to claim 1, characterized in that, The determination of whether the high-frequency oil return condition or the low-frequency oil return condition is met based on the acquired compressor operating status and the relationship between q / Q and a preset ratio includes: When the compressor is running at low frequency, compare whether q / Q is less than the preset ratio A; When q / Q is less than the preset ratio A, it is determined that the low-frequency oil return condition is met. When the compressor is running at high frequency, compare whether q / Q is greater than the preset ratio B; When q / Q is greater than the preset ratio B, it is determined that the high-frequency oil return condition is met.

5. The method according to claim 1, characterized in that, Before obtaining the compressor's operating status, the process also includes: waiting for the compressor to run for a fourth set time.

6. The method according to claim 4, characterized in that, The preset ratio A is 20%, and the preset ratio B is 80%.

7. An oil return system, characterized in that, For performing the method as described in any one of claims 1-6, the oil return system includes a closed-loop oil return unit connected between an oil separator and a compressor.

8. The oil return system according to claim 7, characterized in that, The closed-loop oil return unit includes a closed-loop oil return pipe and an oil return pipe solenoid valve or electronic expansion valve; one end of the closed-loop oil return pipe is connected to the oil separator, and the other end is connected to the oil sump at the bottom of the compressor; the oil return pipe solenoid valve or electronic expansion valve is installed on the closed-loop oil return pipe; or, the closed-loop oil return unit includes a capillary tube, one end of which is connected to the oil separator, and the other end is connected to the oil sump at the bottom of the compressor.

9. A compressor, characterized in that, Includes the oil return system as described in any one of claims 7-8.

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