Oil return control method and device of compressor

Abstract

The invention discloses an oil return control method and device of a compressor. The oil return control method of the compressor comprises the steps that operation parameters of the compressor at different moments are obtained; the operation parameters comprise the rotating speed of the compressor, the bearing pressure difference of the compressor and the lubricating oil temperature of the compressor; determining oil film thicknesses at different moments according to the operating parameters based on a model of the operating parameters and the oil film thicknesses; and the oil return amount of the compressor is controlled according to the oil film thicknesses at different moments. The realizability of obtaining the oil film thickness can be improved, and meanwhile the cost of obtaining the oil film thickness can be reduced. Moreover, the three-parameter model can guarantee the measurement precision of the oil film thickness, enables the process of obtaining the oil film thickness to have good system reliability and environmental adaptability, and facilitates the realization of industrialization. The oil return precision of the compressor can be improved, the risk of dry friction of a bearing of the compressor and the requirement for the circulation amount of lubricating oil are reduced, and the reliability of the compressor is improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of air conditioners, and particularly to an oil return control method and device for a compressor. Background Art

[0002] With the development of the air conditioner industry, the requirements for the reliability of air conditioners are getting higher and higher. The reliability of the compressor is an important part of the reliability of the air conditioner. At present, the oil return methods of the compressor include the differential pressure oil return method and the timed oil return method. When the differential pressure oil return method is adopted, it is easy to cause the oil return of the compressor to lag, resulting in lubrication failure and increasing the risk of dry friction of the compressor bearing. When the timed oil return method is adopted, the oil return timing is inaccurate, which is easy to cause ineffective oil return circulation, increasing the demand for the lubricating oil circulation volume and reducing the reliability of the compressor. Summary of the Invention

[0003] The present invention provides an oil return control method and device for a compressor, so as to improve the oil return control accuracy of the compressor, reduce the risk of dry friction of the compressor bearing and the demand for the lubricating oil circulation volume, and improve the reliability of the compressor.

[0004] In a first aspect, an embodiment of the present invention provides an oil return control method for a compressor, including:

[0005] Obtaining the operating parameters of the compressor at different times; the operating parameters include the rotational speed of the compressor, the bearing differential pressure of the compressor, and the lubricating oil temperature of the compressor.

[0006] Determining the oil film thickness at different times according to the operating parameters based on a model of the operating parameters and the oil film thickness;

[0007] Controlling the oil return amount of the compressor according to the oil film thickness at different times.

[0008] Optionally, determining the oil film thickness at different times according to the operating parameters based on a model of the operating parameters and the oil film thickness includes:

[0009] δ = K × n α × T_oil -β × ΔP γ ;

[0010] wherein, δ is the oil film thickness at the current time, n is the rotational speed of the compressor at the current time, T_oil is the discharge oil temperature of the exhaust pipe of the compressor at the current time, ΔP is the bearing differential pressure of the compressor at the current time, K is the characteristic constant of the oil return control device of the compressor, α is the exponential coefficient of the rotational speed of the compressor, β is the exponential coefficient of the discharge oil temperature of the exhaust pipe of the compressor, and γ is the exponential coefficient of the bearing differential pressure of the compressor.

[0011] Optionally, the operating parameters include a bearing pressure difference of the compressor, and obtaining the operating parameters of the compressor at different times includes:

[0012] Obtaining the circumferential pressure of the bearing seat of the compressor at different times for at least two weeks; the circumferential pressure for each week includes at least two pressure values, and the at least two pressure values ​​are used to characterize the pressure at different positions of the bearing seat of the compressor within one week along the circumference;

[0013] Determine the weekly average circumferential pressure and the circumferential pressure difference in any week based on the circumferential pressure for at least two weeks;

[0014] The axial pressure difference is determined according to the difference of the circumferential average pressures at different circumferences;

[0015] A bearing pressure difference of the compressor is determined based on the circumferential pressure difference and the axial pressure difference.

[0016] Optionally, determining the weekly average circumferential pressure and the circumferential pressure difference of any week based on the circumferential pressure of at least two weeks comprises:

[0017] The geometric mean of the weekly circumferential pressure is taken as the weekly circumferential average pressure;

[0018] The circumferential pressure difference is determined according to the extreme difference of the circumferential pressure in any one circumference.

[0019] Optionally, the circumferential pressure of the bearing seat includes two weeks, and the position of the bearing seat represented by the circumferential pressure of the first week is closer to the bearing of the compressor than the position of the bearing seat represented by the circumferential pressure of the second week; determining the axial pressure difference according to the difference of the circumferential average pressures of different weeks includes:

[0020] ΔPa=(P2-P1)×K geo ;

[0021] Wherein, ΔPa is the axial pressure difference, P2 is the circumferential average pressure of the second cycle, P1 is the circumferential average pressure of the first cycle, K geo K is the geometric correction coefficient of the axial pressure difference: geo =L1 / L2; L1 is the effective length of the actual oil circuit of the compressor, and L2 is the designed nominal length of the compressor.

[0022] Optionally, determining the bearing pressure difference of the compressor according to the circumferential pressure difference and the axial pressure difference includes:

[0023]

[0024] Among them, ΔP is the bearing pressure difference, ΔPa is the axial pressure difference, ΔPc is the circumferential pressure difference, and Cd is the dynamic correction coefficient of the bearing pressure difference.

[0025] Optionally, controlling the oil return amount of the compressor according to the oil film thickness at different times includes:

[0026] Determine the deviation value of the oil film thickness according to the oil film thickness at the current moment and the oil film thickness target value, and determine the deviation change rate of the oil film thickness according to the oil film thickness at the current moment and the oil film thickness at the previous moment;

[0027] The opening degree of the oil return solenoid valve of the compressor is determined based on fuzzy control according to the deviation value of the oil film thickness and the deviation change rate, so as to control the oil return amount of the compressor.

[0028] Optionally, after determining the oil film thickness at different times according to the operating parameter based on the model of the operating parameter and the oil film thickness, the method further includes:

[0029] When the oil film thickness at the current moment is less than a first preset value, an alarm signal is output and the oil return frequency of the compressor is increased;

[0030] When the oil film thickness at the current moment is less than the second preset value and the duration is greater than the first time, the compressor is controlled to stop; and the second preset value is less than the first preset value.

[0031] Optionally, the oil return control method of the compressor further includes:

[0032] Obtain the oil mist concentration in the compressor exhaust pipe;

[0033] When the oil mist concentration is greater than a third preset value, the compressor is supplemented with oil.

[0034] In a second aspect, an embodiment of the present invention further provides an oil return control device for a compressor, comprising:

[0035] An acquisition module, used to acquire operating parameters of the compressor at different times; the operating parameters include the rotation speed of the compressor, the bearing pressure difference of the compressor and the lubricating oil temperature of the compressor;

[0036] An oil film thickness determination module, used for determining the oil film thickness at different times based on the operating parameters and a model of the oil film thickness;

[0037] A control module is used to control the oil return amount of the compressor according to the oil film thickness at different times.

[0038] The technical solution of the embodiment of the present invention can improve the feasibility of obtaining the oil film thickness and reduce the cost of obtaining the oil film thickness by obtaining the operating parameters of the compressor at different times and then determining the oil film thickness at different times based on the operating parameters and the model of the oil film thickness. Moreover, the three-parameter model can ensure the measurement accuracy of the oil film thickness and make the process of obtaining the oil film thickness have good system reliability and environmental adaptability, which is conducive to industrialization. Then, the oil return amount of the compressor is controlled according to the oil film thickness at different times, which improves the oil return accuracy of the compressor, thereby reducing the risk of dry friction of the compressor bearing and the circulation demand of the lubricating oil, and improving the reliability of the compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A flowchart of a compressor oil return control method provided by an embodiment of the present invention;

[0040] Figure 2 A flow chart of another oil return control method for a compressor provided by an embodiment of the present invention;

[0041] Figure 3 A schematic diagram of the distribution of pressure sensors on a bearing seat provided by an embodiment of the present invention;

[0042] Figure 4 A flow chart of another oil return control method for a compressor provided by an embodiment of the present invention;

[0043] Figure 5 A schematic structural diagram of an oil return control device for a compressor provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0045] An embodiment of the present invention provides a compressor oil return control method for controlling the oil return amount of the compressor. Specifically, the oil return system of the compressor includes an oil return pipeline, an oil return solenoid valve and an oil separator. One end of the oil return pipeline is connected to the return air pipeline of the compressor, and the other end of the oil return pipeline is connected to the exhaust pipeline of the compressor through the oil separator, and the oil return solenoid valve is installed on the oil return pipeline. After the oil separator separates the oil and gas in the exhaust of the compressor, the oil can return to the compressor through the oil return pipeline to realize the oil return of the compressor, and the oil return amount of the compressor is controlled by the opening of the oil return solenoid valve. Figure 1The flowchart of a compressor oil return control method provided by an embodiment of the present invention can be executed by a compressor oil return control device. When the compressor oil return control device is applied to an air conditioner, the compressor oil return control device can be integrated into the controller of the air conditioner. Figure 1 As shown, the method includes:

[0046] S110, obtaining operating parameters of the compressor at different times; the operating parameters include the speed of the compressor, the bearing pressure difference of the compressor, and the lubricating oil temperature of the compressor;

[0047] Among them, the operating parameters of the compressor can characterize the thickness of the oil film. For example, the thickness of the oil film is positively correlated with the rotation speed of the compressor. The faster the rotation speed of the compressor, the thicker the oil film thickness. The lubricating oil temperature of the compressor is also positively correlated with the thickness of the oil film. The higher the lubricating oil temperature of the compressor, the lower the viscosity of the lubricating oil, and the thinner the oil film thickness. The bearing pressure difference of the compressor can characterize the oil film pressure distribution in the load-bearing area, which is sensitive to the change of the oil film thickness. The bearing pressure difference of the compressor is positively correlated with the oil film thickness. When obtaining the operating parameters of the compressor, the speed of the compressor can be obtained through the feedback of the frequency converter of the compressor. At this time, the compressor speed fed back by the frequency converter can be obtained by the sensor. In addition, an oil temperature sensor can be provided in the oil pipeline of the compressor to obtain the lubricating oil temperature of the compressor. A pressure difference sensor can be provided on the bearing seat of the compressor to obtain the bearing pressure difference of the compressor. When obtaining the operating parameters of the compressor at different times, the operating parameters of the compressor can be dynamically obtained at different times to ensure the accuracy of the obtained operating parameters, and at the same time, the change trend of different operating parameters can be determined. The time interval between the operating parameters at different times can be set according to demand. For example, the time interval between the operating parameters at different times can be a preset time that is set in advance.

[0048] S120, determining the oil film thickness at different times according to the operating parameters based on a model of the operating parameters and the oil film thickness;

[0049] Among them, the model of operating parameters and oil film thickness can be a pre-set model. After obtaining the operating parameters, the operating parameters are used as the input of the model of operating parameters and oil film thickness, so that the model of operating reference and oil film thickness determines the oil film thickness according to the operating parameters. When the acquired operating parameters are operating parameters at different times, the model of operating parameters and oil film thickness can determine the oil film thickness at different times according to the operating parameters at different times. When the operating parameters include the speed of the compressor, the bearing pressure difference of the compressor and the lubricating oil temperature of the compressor, the model of operating parameters and oil film thickness is a three-parameter model of the speed of the compressor, the bearing pressure difference of the compressor and the lubricating oil temperature of the compressor. The acquisition process of the speed of the compressor, the bearing pressure difference of the compressor and the lubricating oil temperature of the compressor has good feasibility, and the control accuracy is relatively high and the cost is relatively low. Determining the oil film thickness by the model of operating parameters and oil film thickness can improve the feasibility of obtaining the oil film thickness and reduce the cost of obtaining the oil film thickness compared with the solution of directly measuring the oil film thickness. Moreover, the three-parameter model can ensure the measurement accuracy of the oil film thickness, and at the same time, the process of obtaining the oil film thickness has good system reliability and environmental adaptability, which is conducive to industrialization. The oil return control method of the compressor provided in the embodiment of the present invention has significant competitive advantages in terms of energy efficiency improvement, reliability and intelligent level, and is particularly suitable for high-end application scenarios such as data centers, cold chain logistics, industrial refrigeration, etc. that have strict requirements on energy saving and stability.

[0050] S130, controlling the oil return amount of the compressor according to the oil film thickness at different times.

[0051] Among them, after determining the oil film thickness at different times, the oil return amount of the compressor can be controlled according to the changing trend of the oil film thickness, so that the oil return amount of the compressor meets the needs of the compressor. At the same time, the accuracy of the oil return timing of the compressor can be improved, and the oil return accuracy of the compressor is improved, thereby reducing the risk of dry friction of the compressor bearings and the circulation volume demand of the lubricating oil, and improving the reliability of the compressor.

[0052] The technical solution of this embodiment can improve the feasibility of obtaining the oil film thickness and reduce the cost of obtaining the oil film thickness by obtaining the operating parameters of the compressor at different times and then determining the oil film thickness at different times based on the operating parameters and the model of the oil film thickness. Moreover, the three-parameter model can ensure the measurement accuracy of the oil film thickness and make the process of obtaining the oil film thickness have good system reliability and environmental adaptability, which is conducive to industrialization. Then, the oil return amount of the compressor is controlled according to the oil film thickness at different times, which improves the oil return accuracy of the compressor, thereby reducing the risk of dry friction of the compressor bearing and the circulation demand of the lubricating oil, and improving the reliability of the compressor.

[0053] In some embodiments, determining the oil film thickness at different times based on the operating parameters and the model of the oil film thickness according to the operating parameters includes:

[0054] δ=K×n α ×T_oil -β ×ΔP γ ;

[0055] Among them, δ is the oil film thickness at the current moment, n is the speed of the compressor at the current moment, T_oil is the discharge oil temperature of the compressor exhaust pipe at the current moment, ΔP is the bearing pressure difference of the compressor at the current moment, K is the characteristic constant of the oil return control device of the compressor, α is the exponential coefficient of the compressor speed, β is the exponential coefficient of the discharge oil temperature of the compressor exhaust pipe, and γ is the exponential coefficient of the bearing pressure difference of the compressor.

[0056] Specifically, the characteristic constant K of the compressor, the characteristic constant α of the compressor, the exponential coefficient β of the discharge oil temperature of the compressor exhaust pipe, and the exponential coefficient γ of the bearing pressure difference of the compressor are all constants, and their specific numerical ranges can be determined through theoretical modeling, experimental calibration, engineering correction and other processes. Exemplarily, the value range of the characteristic constant K of the compressor can be 0.8-1.2, the value range of the characteristic constant α of the compressor can be 0.35±0.05, the value range of the exponential coefficient β of the discharge oil temperature of the compressor exhaust pipe can be 0.18±0.03, and the value range of the exponential coefficient γ of the bearing pressure difference of the compressor can be 0.25±0.02. At this time, the oil film thickness is a power function of the three parameters of the speed of the compressor, the bearing pressure difference of the compressor, and the lubricating oil temperature of the compressor, which improves the accuracy of the model of the operating parameters and the oil film thickness, so that after obtaining the operating parameters of the compressor and determining the oil film thickness based on the operating parameters and the model of the oil film thickness, the measurement accuracy of the oil film thickness is improved, the control accuracy of the oil return amount of the compressor is improved, and the accuracy of the compressor is improved.

[0057] In some embodiments, the operating parameter includes a bearing pressure differential of the compressor. Figure 2 A flowchart of another compressor oil return control method provided by an embodiment of the present invention, such as Figure 2 As shown, the method includes:

[0058] S210, obtaining circumferential pressures of the bearing seat of the compressor for at least two weeks at different times; each circumferential pressure includes at least two pressure values, and the at least two pressure values ​​are used to characterize the pressures at different positions of the bearing seat of the compressor within one week along the circumference;

[0059] Wherein, when the operating parameters include the bearing pressure difference of the compressor, the bearing pressure difference of the compressor can be obtained through the bearing pressure difference sensor array. The bearing pressure difference sensor array includes at least two pressure sensors, each pressure sensor includes at least two pressure sensors, which are respectively used to obtain the pressure values ​​at different circumferential positions of the bearing seat, so that the circumferential pressure of the bearing seat along one week can be determined based on the pressure sensors at different circumferential positions of the bearing seat. Similarly, the circumferential pressure of the bearing seat along at least two weeks can be determined by at least two pressure sensors. Exemplarily, Figure 3 A schematic diagram of the distribution of pressure sensors on a bearing seat provided by an embodiment of the present invention. Figure 3 As shown, two weeks of pressure sensors 10 are arranged on the bearing seat of the compressor, and each week of pressure sensor 10 includes four pressure sensors 101. The four pressure sensors 101 can be evenly distributed along the circumference of the bearing seat, that is, the interval between adjacent pressure sensors 101 is 90°. At this time, multiple pressure values ​​of the circumferential pressure of each week can be obtained through four pressure sensors 101 on a week to determine the circumferential pressure of the bearing seat along the circumference. At this time, the circumferential pressure of one week includes four pressure values. Among them, the pressure sensor 101 can be a micro-electromechanical system (MEMS) piezoelectric film sensor, and its accuracy range is ±0.5%, and the sampling frequency is 1kHz.

[0060] S220, determining the weekly average circumferential pressure and the circumferential pressure difference of any week based on the circumferential pressure of at least two weeks;

[0061] The weekly circumferential pressure includes at least two pressure values. After determining the circumferential pressure for at least two weeks, the weekly circumferential average pressure can be determined based on at least two pressure values ​​in the weekly circumferential pressure. For example, when determining the weekly circumferential average pressure based on the circumferential pressure for at least two weeks, the geometric mean of the weekly circumferential pressure can be used as the weekly circumferential average pressure. The circumferential average pressure at this time can weaken the effect of uneven circumferential distribution of lubricating oil in the bearing seat on the oil film thickness. For example, continue to refer to Figure 3 When the weekly pressure sensor 10 includes four pressure sensors 101, the weekly circumferential pressure includes four pressure values. At this time, the geometric mean of the four pressure values ​​can be calculated as the circumferential average pressure. For example, the pressure values ​​of the four pressure sensors 101 of the first weekly pressure sensor 10 are P 1,1 , P 1,2 , P 1,3 and P 1,4 The average circumferential pressure in the first cycle is Similarly, the pressure values ​​of the four pressure sensors 101 of the second cycle pressure sensor 10 are P 2,1 , P 2,2 , P2,3 and P 2,4 The average circumferential pressure in the second cycle is For example, Table 1 is a table of pressure values ​​of eight pressure sensors 101 of a two-week pressure sensor 10 provided by an embodiment of the present invention. As shown in Table 1, when the pressure values ​​P of the four pressure sensors 101 of the first-week pressure sensor 10 are 1,1 , P 1,2 , P 1,3 and P 1,4 When the circumferential average pressure of the first cycle is 520.3 kPa, 518.7 kPa, 515.9 kPa and 510.2 kPa respectively, When the pressure values ​​P of the four pressure sensors 101 of the second pressure sensor 10 are 2,1 , P 2,2 , P 2,3 and P 2,4 When the circumferential average pressure of the second cycle is 505.1 kPa, 503.8 kPa, 507.2 kPa and 498.4 kPa respectively,

[0062] Table 1

[0063] First cycle circumferential pressure (kPa) Second cycle circumferential pressure (kPa) 520.3 505.1 518.7 503.8 515.9 507.2 510.2 498.4

[0064] After determining the circumferential pressure of at least two weeks, the circumferential pressure difference can be determined based on at least two pressure values ​​within the circumferential pressure of any week, that is, the circumferential pressure difference can be determined based on the circumferential pressure of any week. Exemplarily, the circumferential pressure difference can be determined based on the extreme difference of the circumferential pressure of any week, that is, the circumferential pressure difference can be the difference between the maximum and minimum values ​​of at least two pressure values ​​of the circumferential pressure of one week. The circumferential pressure difference at this time can evaluate the circumferential non-uniformity of the lubricating oil in the bearing seat. When the circumferential pressure difference is too large, it can indicate uneven wear of the bearing or blockage of the oil circuit. Exemplarily, continue to refer to Figure 3 When the pressure sensor 10 includes four pressure sensors 101 per week, the pressure values ​​of the four pressure sensors 101 of the pressure sensor 10 in the first week are P 1,1 , P 1,2 , P 1,3 and P 1,4 The circumferential pressure difference of the first cycle ΔPc1=max(P 1,1 , P 1,2 , P 1,3 and P 1,4 )-min(P 1,1 , P 1,2 , P 1,3 and P 1,4 ). The pressure values ​​of the four pressure sensors 101 of the second week pressure sensor 10 are P 2,1 , P 2,2, P 2,3 and P 2,4 The circumferential pressure difference of the second cycle ΔPc1=max(P 2,1 , P 2,2 , P 2,3 and P 2,4 )-min(P 2,1 , P 2,2 , P 2,3 and P 2,4 ). At this time, the circumferential pressure difference may be the circumferential pressure difference ΔPc1 of the first cycle, or may be the circumferential pressure difference ΔPc2 of the second cycle, which is not limited here.

[0065] For example, referring to Table 1, when the pressure values ​​P of the four pressure sensors 101 of the pressure sensor 10 in the first week are 1,1 , P 1,2 , P 1,3 and P 1,4 When the circumferential pressure difference of the first cycle is ΔPc1=max(P 1,1 , P 1,2 , P 1,3 and P 1,4 )-min(P 1,1 , P 1,2 , P 1,3 and P 1,4 )=520.3-510.2=10.1kPa.

[0066] In some embodiments, continue to refer to Figure 3 , the pressure sensor 101 of the first week is closer to the geometric center of the bearing seat relative to the pressure sensor 101 of the second week, that is, the pressure sensor 101 of the first week is closer to the rotor of the compressor relative to the pressure sensor 101 of the second week. Exemplarily, the axial spacing between the pressure sensor 101 of the first week and the pressure sensor 101 of the second week can be 10 mm. At this time, the circumferential pressure difference of the first week can directly reflect the distribution of the oil film pressure in the load-bearing area, and its dynamic response to the change of the oil film thickness is fast, making it sensitive to the change of the oil film thickness. When the circumferential pressure difference adopts the circumferential pressure difference of the first week, the measurement accuracy of the oil film thickness can be improved. The circumferential pressure difference of the second week is greatly affected by the downstream pipeline, and can reflect the pressure state of the oil circuit outlet.

[0067] S230, determining the axial pressure difference according to the difference of the circumferential average pressures at different circumferences;

[0068] The axial pressure difference can be determined according to the difference between any two circumferential average pressures. For example, the circumferential pressure difference can be determined according to the difference between the circumferential average pressure determined by the circumferential pressure sensor closest to the compressor rotor and the circumferential average pressure determined by the circumferential pressure sensor farthest from the compressor rotor.

[0069] Continue to refer Figure 3 The circumferential pressure of the bearing seat includes two weeks, and the position of the bearing seat characterized by the circumferential pressure of the first week is closer to the bearing of the compressor relative to the position of the bearing seat characterized by the circumferential pressure of the second week, that is, the pressure sensor 101 of the first week is closer to the rotor of the compressor relative to the pressure sensor 101 of the second week. The axial pressure difference is determined according to the difference of the circumferential average pressure of different weeks, including:

[0070] ΔPa=(P2-P1)×K geo ;

[0071] Where ΔPa is the axial pressure difference, P2 is the average circumferential pressure of the second cycle, P1 is the average circumferential pressure of the first cycle, and K geo K is the geometric correction factor of the axial pressure difference: geo =L1 / L2; L1 is the effective length of the actual oil circuit of the compressor, and L2 is the designed nominal length of the compressor.

[0072] Among them, K geo is the geometric correction coefficient of the axial pressure difference, and its numerical range can be determined based on the finite element analysis of the bearing oil channel structure. For example, the geometric correction coefficient K of the axial pressure difference is geo The value range of can be 0.8-1.2. After determining the circumferential average pressure of the first week and the circumferential average pressure of the second week, the circumferential pressure difference can be determined according to the product of the difference between the two and the geometric correction coefficient of the axial pressure difference. For example, referring to Table 1, the circumferential average pressure of the first week is Average circumferential pressure in the second week When the geometric correction factor K of the axial pressure difference geo When =0.95, the axial pressure difference ΔPa=(503.6-516.2)×0.95=-12.0kPa.

[0073] S240: Determine the bearing pressure difference of the compressor according to the circumferential pressure difference and the axial pressure difference.

[0074] Among them, after the circumferential pressure difference and the circumferential pressure difference are determined, the circumferential pressure difference and the circumferential pressure difference can be weighted and synthesized to determine the bearing pressure difference of the compressor.

[0075] Exemplarily, determining the bearing pressure difference of the compressor according to the circumferential pressure difference and the axial pressure difference includes:

[0076]

[0077] Among them, ΔP is the bearing pressure difference, ΔPa is the axial pressure difference, ΔPc is the circumferential pressure difference, and Cd is the dynamic correction coefficient of the bearing pressure difference.

[0078] The dynamic correction coefficient of the bearing pressure difference can be calibrated by experiment. For example, the dynamic correction coefficient Cd of the bearing pressure difference can be in the range of 0.9-1.1. Figure 3 According to Table 1, the circumferential pressure difference of the first cycle can be used as the circumferential pressure difference of the compressor, that is, the circumferential pressure difference ΔPc = max(P 1,1 , P 1,2 , P 1,3 and P 1,4 )-min(P 1,1 , P 1,2 , P 1,3 and P 1,4 )=520.3-510.2=10.1kPa. At the same time, the axial pressure difference ΔPa=(503.6-516.2)×0.95=-12.0kPa. When the dynamic correction coefficient of the bearing pressure difference Cd=1.05, the bearing pressure difference of the compressor

[0079] S250, determining the oil film thickness at different times according to the operating parameters based on a model of the operating parameters and the oil film thickness;

[0080] S260, controlling the oil return amount of the compressor according to the oil film thickness at different times.

[0081] It should be noted that the operating parameters include the speed of the compressor, the bearing pressure difference of the compressor and the lubricating oil temperature of the compressor. When obtaining the bearing pressure difference of the compressor, the lubricating oil temperature of the compressor can be simultaneously obtained through the oil temperature sensor, and the speed of the compressor can be synchronously fed back through the inverter, so that the speed of the compressor, the bearing pressure difference of the compressor and the lubricating oil temperature of the compressor are obtained at the same time, so that the compressor obtains different operating parameters at the same time, ensuring the consistency of the acquisition time of different operating parameters.

[0082] In some embodiments, the oil return control device of the compressor may also include an acoustic emission probe installed in a vibration sensitive area of ​​the compressor housing. The acoustic emission probe uses a wideband sensor with a frequency range of 50-400kHz, and can extract the contact characteristic frequency of the compressor rotor through wavelet packet decomposition, so as to determine the current analysis speed of the compressor rotor. When the deviation between the current analysis speed and the compressor speed fed back by the frequency converter is greater than the preset speed value, the calibration alarm of the sensor for obtaining the compressor speed fed back by the frequency converter can be triggered, thereby ensuring the reliability of the obtained compressor speed. Exemplarily, the preset speed value can be 2%, that is, when the difference between the compressor speed fed back by the frequency converter and the speed analyzed by the acoustic emission probe is greater than the ratio of the speed analyzed by the acoustic emission probe to the speed analyzed by the acoustic emission probe is greater than 2%, the calibration alarm of the sensor for obtaining the compressor speed fed back by the frequency converter is triggered.

[0083] In some embodiments, Figure 4 A flowchart of another compressor oil return control method provided by an embodiment of the present invention, such as Figure 4 As shown, the method includes:

[0084] S310, obtaining operating parameters of the compressor at different times; the operating parameters include the speed of the compressor, the bearing pressure difference of the compressor, and the lubricating oil temperature of the compressor;

[0085] S320, determining the oil film thickness at different times according to the operating parameters based on a model of the operating parameters and the oil film thickness;

[0086] S330, determining a deviation value of the oil film thickness according to the oil film thickness at the current moment and the target value of the oil film thickness, and determining a deviation change rate of the oil film thickness according to the oil film thickness at the current moment and the oil film thickness at the previous moment;

[0087] Among them, when the operating parameters are dynamically acquired, the oil film thickness corresponding to the moment can be determined based on the operating parameters at each moment based on the model of the operating parameters and the oil film thickness, that is, the oil film thickness at different moments can be determined based on the operating parameters at different moments. The target value of the oil film thickness can be determined according to the thickness of the lubricating oil required by the compressor. Exemplarily, the range of the target value of the oil film thickness can be 12-18 μm, and preferably, the target value of the oil film thickness can be 15 μm. After the oil film thickness at the current moment is determined based on the model of the operating parameters and the oil film thickness at the current moment, the deviation value of the oil film thickness at the current moment can be determined according to the difference between the oil film thickness at the current moment and the target value of the oil film thickness. At the same time, the deviation change rate of the oil film thickness can be determined according to the change rate of the oil film thickness at the current moment and the oil film thickness at the previous moment to characterize the change rate of the oil film thickness. Exemplarily, the time interval between adjacent moments can be a preset time. The difference between the oil film thickness at the current moment and the oil film thickness at the previous moment, divided by the preset time, is the deviation change rate of the oil film thickness.

[0088] S340. Determine the opening of the oil return solenoid valve of the compressor based on fuzzy control according to the deviation value and the deviation change rate of the oil film thickness to control the oil return amount of the compressor.

[0089] Among them, before determining the opening of the oil return solenoid valve based on fuzzy control, a fuzzy rule base can be established. Then, after determining the deviation value and deviation change rate of the oil film thickness, the opening of the oil return solenoid valve is directly determined according to the fuzzy rule base to adjust the oil return amount of the compressor, thereby improving the oil return accuracy of the compressor, thereby reducing the risk of dry friction of the compressor bearing and the circulation volume demand of the lubricating oil, and improving the reliability of the compressor.

[0090] Exemplarily, Table 2 is a schematic table of a fuzzy rule base provided by an embodiment of the present invention, wherein the deviation value e of the oil film thickness is divided into five levels, namely, NB1, NS1, ZO1, PS1 and PB1. The different levels of the deviation value e of the oil film thickness can be determined by setting a preset deviation value range. Among them, the NB1 level is used to characterize the deviation value e of the oil film thickness as a negative number and a relatively large absolute value, the NS1 level is used to characterize the deviation value e of the oil film thickness as a negative number and a relatively small absolute value, the ZO1 level is used to characterize the deviation value e of the oil film thickness as 0, the PS1 level is used to characterize the deviation value e of the oil film thickness as a positive number and a relatively small number, and the PB1 level is used to characterize the deviation value e of the oil film thickness as a positive number and a relatively large number. The deviation change rate ec of the oil film thickness is also divided into five levels, namely, NB2, NS2, ZO2, PS2 and PB2, and the different levels of the deviation change rate ec of the oil film thickness can be determined by setting a preset deviation change rate range. Among them, the NB2 level is used to characterize the deviation change rate ec of the oil film thickness as a negative number with a relatively large absolute value, the NS2 level is used to characterize the deviation change rate ec of the oil film thickness as a negative number with a relatively small absolute value, the ZO2 level is used to characterize the deviation change rate ec of the oil film thickness as 0, the PS2 level is used to characterize the deviation change rate ec of the oil film thickness as a positive number with a relatively small value, and the PB2 level is used to characterize the deviation change rate ec of the oil film thickness as a positive number with a relatively large value. At this time, the opening of the return oil solenoid valve is divided into seven levels according to 0-100%, namely NB3, NM3, NS3, ZO3, PS3, PM3 and PB3. Among them, the NB3 level is used to characterize that the opening of the return oil solenoid valve is located at a position slightly smaller than the middle position of the opening range, and the difference with the middle position of the opening range is the largest. The NM3 level is used to characterize that the opening of the return oil solenoid valve is located at a position slightly smaller than the middle position of the opening range, and the difference with the middle position of the opening range is smaller than the difference between NB3 and the middle position of the opening range. The NS3 level is used to characterize that the opening of the return oil solenoid valve is located at a position slightly smaller than the middle position of the opening range, and the difference with the middle position of the opening range is smaller than the difference between NM3 and the middle position of the opening range. The ZO3 level is used to characterize that the opening of the return oil solenoid valve is located in the middle position of the opening range. The PS3 level is used to characterize that the opening of the return oil solenoid valve is located at a position slightly larger than the middle position of the opening range, and the difference with the middle position of the opening range is the smallest. The PM3 level is used to characterize that the opening of the return oil solenoid valve is located at a position slightly larger than the middle position of the opening range, and the difference with the middle position of the opening range is greater than the difference between PS3 and the middle position of the opening range. The PB3 level is used to characterize that the opening of the return oil solenoid valve is located at a position slightly larger than the middle position of the opening range, and the difference with the middle position of the opening range is greater than the difference between PM3 and the middle position of the opening range.

[0091] Table 2

[0092] e / ec NB2 NS2 ZO2 PS2 PB2 NB1 PB3 PB3 PM3 PS3 PS3 NS1 PB3 PM3 PS3 PS3 NS3 ZO1 PM3 PS3 PS3 NS3 NM3 PS1 PS3 PS3 NS3 NM3 NB3 PB1 PS3 NS3 NM3 NB3 NB3

[0093] As shown in Table 2, after determining the current level of the oil film thickness and the current level of the deviation change rate according to the deviation value and the deviation change rate of the oil film thickness, respectively, the opening level of the return oil solenoid valve can be directly determined according to the fuzzy rule base. For example, when the level of the deviation value e of the oil film thickness is NB1, the oil film thickness is relatively thin. And when the level of the deviation change rate ec of the oil film thickness is NB2, the oil film thickness at the current moment is thinner than the oil film thickness at the previous moment, that is, the oil film thickness is getting thinner and thinner. At this time, the opening level of the return oil solenoid valve can be controlled to PB3, that is, the opening of the return oil solenoid valve reaches the maximum level, increasing the oil return amount of the compressor, improving the oil return accuracy of the compressor, reducing the risk of dry friction of the compressor bearing and the circulation demand of the lubricating oil, and improving the reliability of the compressor.

[0094] It should be noted that the classification of the deviation value of the oil film thickness, the classification of the deviation change rate of the oil film thickness, and the classification of the opening of the oil return solenoid valve can be set as needed and are not limited here. In addition, when adjusting the opening of the oil return solenoid valve according to the deviation value and the deviation change rate of the oil film thickness, the holding time of the opening of the oil return solenoid valve can be determined according to the control cycle of the oil return solenoid valve. For example, if the control cycle of the oil return solenoid valve is 0.5-2 seconds, the holding time of the opening of the oil return solenoid valve can be 0.5-2 seconds.

[0095] In some embodiments, after determining the oil film thickness at different times based on the operating parameters and the model of the oil film thickness, the method further includes:

[0096] When the compressor is in an abnormal operating state, the emergency oil return mode is activated. At this time, the opening of the oil return solenoid valve can be set to 100% and the duration is 10-30 seconds to reduce the risk of abnormal operation of the compressor at the next moment. The abnormal operating state of the compressor can be an abnormal condition of the oil film thickness. For example, the oil film thickness is very thin.

[0097] In some embodiments, after determining the oil film thickness at different times based on the operating parameters and the model of the oil film thickness, the method further includes:

[0098] When the oil film thickness at the current moment is less than the first preset value, an alarm signal is output and the oil return frequency of the compressor is increased;

[0099] Among them, the first preset value may be less than or equal to the range of the oil film thickness corresponding to the minimum level of the deviation value of the oil film thickness. Exemplarily, referring to Table 2, the minimum level of the deviation value of the oil film thickness may be NB1 level, at which point the first preset value is less than or equal to the oil film thickness corresponding to the minimum value of the deviation value of the oil film thickness of NB1 level, that is, within the deviation value range of the oil film thickness corresponding to NB1 level, the oil film thickness minus the oil film thickness target value is the oil film thickness when the minimum deviation value corresponding to NB1 level is. Specifically, when the range of the deviation value of the oil film thickness corresponding to the minimum level NB1 of the deviation value of the oil film thickness is -7μm to -3.5μm, within this range, the minimum value of the deviation value of the oil film thickness is -7μm. When the target value of the oil film thickness is 15μm, the oil film thickness corresponding to the minimum value of the deviation value of the oil film thickness is 8μm, at which point the first preset value may be 8μm. When the current oil film thickness is less than the first preset value, the current oil film thickness of the compressor is too thin. At this time, an alarm can be triggered, an alarm signal can be output, and the oil return frequency of the compressor can be increased, the oil return volume of the compressor can be increased, the risk of dry friction of the compressor bearings can be reduced, and the reliability of the compressor can be improved.

[0100] When the oil film thickness at the current moment is less than the second preset value and the duration is greater than the first time, the compressor is controlled to stop; the second preset value is less than the first preset value.

[0101] Among them, the second preset value is less than the first preset value. When the oil film thickness at the current moment is less than the second preset value, the current oil film thickness of the compressor is thinner. When the duration of the oil film thickness at the current moment being less than the second preset value is greater than the first time, the oil return control process of the compressor cannot effectively increase the oil film thickness of the compressor. At this time, the compressor can be forced to shut down to avoid failure or damage of the compressor bearing due to dry friction. Exemplarily, when the first preset value is 8μm, the second preset value can be 5μm, and the first time can be 10 seconds.

[0102] In some embodiments, the oil return control method of the compressor further includes:

[0103] Obtain the oil mist concentration in the compressor exhaust pipe;

[0104] Among them, the oil return control device of the compressor may also include an oil mist sensor. The oil mist sensor is arranged on the exhaust pipe of the compressor. Exemplarily, the oil mist sensor may be a high-frequency oil mist sensor with a response time of ≤10ms and a measuring range of 0-500ppm. The oil mist sensor may be installed at a distance of 1.5D from the outlet of the exhaust pipe of the compressor, where D is the diameter of the exhaust pipe of the compressor. During the oil return control process of the compressor, the oil mist concentration of the exhaust pipe of the compressor may be obtained through the oil mist sensor to characterize the amount of lubricating oil entering the refrigeration cycle system. The higher the oil mist concentration, the more lubricating oil enters the refrigeration cycle system, the more the amount of oil in the oil pool decreases, and the thinner the oil film thickness is, thereby affecting the stability of the oil film.

[0105] When the oil mist concentration is greater than the third preset value, the compressor is supplemented with oil.

[0106] Among them, the third preset value can be set according to the thickness requirement of the oil film stability. Exemplarily, the third preset value can be 300ppm. When the oil mist concentration is greater than the third preset value, the evaporation of the lubricating oil is too much, resulting in the oil film thickness being too thin. At this time, the oil replenishment program can be triggered to replenish the oil to the compressor. Among them, the return oil volume of the oil replenishment program can be linked with the operating parameters and the oil film thickness model provided in the embodiment of the present invention. Specifically, the oil film thickness at different times can be determined based on the operating parameters and the oil film thickness model according to the operating parameters at different times, and then the return oil volume of the compressor can be controlled according to the oil film thickness at different times to achieve oil replenishment to the compressor.

[0107] An embodiment of the present invention further provides an oil return control device for a compressor. Figure 5 The structure diagram of a compressor oil return control device provided by an embodiment of the present invention is shown in FIG. Figure 5 As shown, the oil return control device of the compressor includes:

[0108] The acquisition module 200 is used to acquire the operating parameters of the compressor at different times; the operating parameters include the speed of the compressor, the bearing pressure difference of the compressor and the lubricating oil temperature of the compressor;

[0109] The oil film thickness determination module 201 is used to determine the oil film thickness at different times based on the operating parameters and the model of the oil film thickness;

[0110] The control module 202 is used to control the oil return amount of the compressor according to the oil film thickness at different times.

[0111] The technical solution of this embodiment obtains the operating parameters of the compressor at different times through the acquisition module, and then the oil film thickness determination module determines the oil film thickness at different times based on the operating parameters and the model of the oil film thickness, which can improve the feasibility of obtaining the oil film thickness and reduce the cost of obtaining the oil film thickness. Moreover, the three-parameter model can ensure the measurement accuracy of the oil film thickness, and at the same time, the process of obtaining the oil film thickness has good system reliability and environmental adaptability, which is conducive to industrialization. Then the control module controls the oil return volume of the compressor according to the oil film thickness at different times, improves the oil return accuracy of the compressor, thereby reducing the risk of dry friction of the compressor bearing and the circulation volume demand of the lubricating oil, and improving the reliability of the compressor.

[0112] In some embodiments, the oil film thickness determination module includes:

[0113] δ=K×n α ×T_oil -β ×ΔP γ ;

[0114] Among them, δ is the oil film thickness at the current moment, n is the speed of the compressor at the current moment, T_oil is the discharge oil temperature of the compressor exhaust pipe at the current moment, ΔP is the bearing pressure difference of the compressor at the current moment, K is the characteristic constant of the oil return control device of the compressor, α is the exponential coefficient of the compressor speed, β is the exponential coefficient of the discharge oil temperature of the compressor exhaust pipe, and γ is the exponential coefficient of the bearing pressure difference of the compressor.

[0115] In some embodiments, the operating parameter includes a bearing pressure difference of the compressor, and the acquisition module includes:

[0116] An acquisition unit is used to acquire the circumferential pressure of the bearing seat of the compressor for at least two weeks at different times; each circumferential pressure includes at least two pressure values, and the at least two pressure values ​​are used to characterize the pressure at different positions of the bearing seat of the compressor within one week along the circumference;

[0117] A first determination unit, configured to determine a weekly circumferential average pressure and a circumferential pressure difference in any week based on circumferential pressures in at least two weeks;

[0118] A second determining unit, configured to determine the axial pressure difference according to the difference in circumferential average pressures at different circumferences;

[0119] The third determining unit is used to determine the bearing pressure difference of the compressor according to the circumferential pressure difference and the axial pressure difference.

[0120] In some embodiments, the first determining unit includes:

[0121] A first calculation subunit is used to take the geometric mean of the weekly circumferential pressure as the weekly circumferential average pressure;

[0122] The second calculation subunit is used to determine the circumferential pressure difference according to the extreme difference of the circumferential pressure in any one circumference.

[0123] In some embodiments, the circumferential pressure of the bearing seat includes two weeks, and the position of the bearing seat represented by the circumferential pressure of the first week is closer to the bearing of the compressor relative to the position of the bearing seat represented by the circumferential pressure of the second week; the second determining unit includes:

[0124] ΔPa=(P2-P1)×K geo ;

[0125] Where ΔPa is the axial pressure difference, P2 is the average circumferential pressure of the second cycle, P1 is the average circumferential pressure of the first cycle, and K geo K is the geometric correction factor of the axial pressure difference: geo =L1 / L2; L1 is the effective length of the actual oil circuit of the compressor, and L2 is the designed nominal length of the compressor.

[0126] In some embodiments, the third determining unit includes:

[0127]

[0128] Among them, ΔP is the bearing pressure difference, ΔPa is the axial pressure difference, ΔPc is the circumferential pressure difference, and Cd is the dynamic correction coefficient of the bearing pressure difference.

[0129] In some embodiments, the control module includes:

[0130] a fourth determining unit, configured to determine a deviation value of the oil film thickness according to the oil film thickness at a current moment and the target value of the oil film thickness, and to determine a deviation change rate of the oil film thickness according to the oil film thickness at a current moment and the oil film thickness at a previous moment;

[0131] The fifth determining unit is used to determine the opening of the oil return solenoid valve of the compressor based on fuzzy control according to the deviation value and the deviation change rate of the oil film thickness, so as to control the oil return amount of the compressor.

[0132] In some embodiments, the oil return control device of the compressor further includes:

[0133] A first emergency module, used to output an alarm signal and increase the oil return frequency of the compressor when the oil film thickness at the current moment is less than a first preset value;

[0134] The second emergency module is used to control the compressor to shut down when the oil film thickness at the current moment is less than a second preset value and the duration is greater than the first time; the second preset value is less than the first preset value.

[0135] In some embodiments, the oil return control device of the compressor further includes:

[0136] An oil mist concentration acquisition module is used to obtain the oil mist concentration of the compressor exhaust pipe;

[0137] The oil replenishing module is used to replenish oil to the compressor when the oil mist concentration is greater than a third preset value.

[0138] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A compressor oil return control method, characterized in that: include: Obtain the operating parameters of the compressor at different times; The operating parameters include the rotation speed of the compressor, the bearing pressure difference of the compressor and the lubricating oil temperature of the compressor; Determining the oil film thickness at different times according to the operating parameters based on a model of the operating parameters and the oil film thickness; The oil return amount of the compressor is controlled according to the oil film thickness at different times.

2. The oil return control method of the compressor according to claim 1, characterized in that: Determining the oil film thickness at different times based on the operating parameters and a model of the oil film thickness includes: δ=K×n α ×T_oil -β ×ΔP γ ; Among them, δ is the oil film thickness at the current moment, n is the speed of the compressor at the current moment, T_oil is the discharge oil temperature of the exhaust pipe of the compressor at the current moment, ΔP is the bearing pressure difference of the compressor at the current moment, K is the characteristic constant of the oil return control device of the compressor, α is the exponential coefficient of the speed of the compressor, β is the exponential coefficient of the discharge oil temperature of the exhaust pipe of the compressor, and γ is the exponential coefficient of the bearing pressure difference of the compressor.

3. The oil return control method for a compressor according to claim 1 or 2, characterized in that: The operating parameters include the bearing pressure difference of the compressor, and obtaining the operating parameters of the compressor at different times includes: Obtaining the circumferential pressure of the bearing seat of the compressor at different times for at least two weeks; the circumferential pressure for each week includes at least two pressure values, and the at least two pressure values ​​are used to characterize the pressure at different positions of the bearing seat of the compressor within one week along the circumference; Determine the weekly average circumferential pressure and the circumferential pressure difference in any week based on the circumferential pressure for at least two weeks; The axial pressure difference is determined according to the difference of the circumferential average pressures at different circumferences; A bearing pressure difference of the compressor is determined based on the circumferential pressure difference and the axial pressure difference.

4. The oil return control method of the compressor according to claim 3, characterized in that: Determining the weekly average circumferential pressure and the circumferential pressure difference in any week based on the circumferential pressure for at least two weeks, comprising: The geometric mean of the weekly circumferential pressure is taken as the weekly circumferential average pressure; The circumferential pressure difference is determined according to the extreme difference of the circumferential pressure in any one circumference.

5. The oil return control method of the compressor according to claim 3, characterized in that: The circumferential pressure of the bearing seat includes two weeks, and the position of the bearing seat represented by the circumferential pressure of the first week is closer to the bearing of the compressor than the position of the bearing seat represented by the circumferential pressure of the second week; The axial pressure difference is determined based on the difference in the circumferential average pressure at different circumferences, including: ΔPa=(P2-P1)×K geo ; Wherein, ΔPa is the axial pressure difference, P2 is the circumferential average pressure of the second cycle, P1 is the circumferential average pressure of the first cycle, K geo K is the geometric correction factor of the axial pressure difference: geo =L1 / L2; L1 is the effective length of the actual oil circuit of the compressor, and L2 is the designed nominal length of the compressor.

6. The oil return control method of the compressor according to claim 3, characterized in that: Determining the bearing pressure difference of the compressor according to the circumferential pressure difference and the axial pressure difference includes: Among them, ΔP is the bearing pressure difference, ΔPa is the axial pressure difference, ΔPc is the circumferential pressure difference, and Cd is the dynamic correction coefficient of the bearing pressure difference.

7. The oil return control method of a compressor according to claim 1, characterized in that: Controlling the oil return amount of the compressor according to the oil film thickness at different times includes: Determine the deviation value of the oil film thickness according to the oil film thickness at the current moment and the oil film thickness target value, and determine the deviation change rate of the oil film thickness according to the oil film thickness at the current moment and the oil film thickness at the previous moment; The opening degree of the oil return solenoid valve of the compressor is determined based on fuzzy control according to the deviation value of the oil film thickness and the deviation change rate, so as to control the oil return amount of the compressor.

8. The oil return control method for a compressor according to claim 1, characterized in that: After determining the oil film thickness at different times according to the operating parameters based on the model of the operating parameters and the oil film thickness, the method further includes: When the oil film thickness at the current moment is less than a first preset value, an alarm signal is output and the oil return frequency of the compressor is increased; When the oil film thickness at the current moment is less than the second preset value and the duration is greater than the first time, the compressor is controlled to stop; and the second preset value is less than the first preset value.

9. The oil return control method of a compressor according to claim 1, characterized in that: Also includes: Obtain the oil mist concentration in the compressor exhaust pipe; When the oil mist concentration is greater than a third preset value, the compressor is supplemented with oil.

10. A compressor oil return control device, characterized in that: include: An acquisition module, used to acquire operating parameters of the compressor at different times; the operating parameters include the rotation speed of the compressor, the bearing pressure difference of the compressor and the lubricating oil temperature of the compressor; An oil film thickness determination module, used for determining the oil film thickness at different times based on the operating parameters and a model of the oil film thickness; A control module is used to control the oil return amount of the compressor according to the oil film thickness at different times.

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