A method for controlling oil return of a multi-connected machine

Abstract

This invention provides a multi-split air conditioning system oil return control method. For systems with multiple outdoor units connected in parallel, the oil return frequency of each outdoor unit is adjusted based on the intake superheat data, thereby achieving on-demand oil distribution. This method is based on a multi-split air conditioning system including at least one outdoor unit, and includes the following steps: acquiring outdoor unit intake superheat data within the oil return cycle; and adjusting the oil return cycle based on the outdoor unit intake superheat data within the oil return cycle.

Description

Technical Field

[0001] This invention relates to a method for controlling oil return in multi-split air conditioning systems, belonging to the field of air conditioning technology. Background Technology

[0002] During the operation of a multi-split air conditioning system, lubricating oil is essential to ensure the normal and reliable operation of the compressor. However, due to the long piping between the indoor and outdoor units and the large number of indoor units, as well as the complex installation conditions, some lubricating oil may be discharged from the compressor and enter the piping and indoor units during operation. Therefore, after a period of operation, the multi-split system must undergo an oil return cycle to allow the lubricating oil in the piping and indoor units to return to the compressor.

[0003] The basic principle of oil return circulation is: high flow rate and return liquid carry back lubricating oil. High flow rate can flush the pipe wall and carry back the lubricating oil in the pipe. Since lubricating oil and liquid refrigerant are miscible, lubricating oil can also be carried back during the return liquid.

[0004] During oil return circulation, in order to ensure a high refrigerant flow rate, the compressor will increase its frequency to a higher flow rate; however, after the compressor increases its frequency, the compressor's own oil discharge will also increase. When the compressor's oil return is greater than its oil discharge, the amount of lubricating oil in the compressor will increase.

[0005] The time interval between two oil return cycles is called the oil return cycle. The current oil return cycle is set to a fixed time, such as 6h or 8h. When the compressor is running at high frequency, the oil return cycle time is long, such as 12h. When the compressor is running at low frequency, the oil return cycle time is short, such as 2h.

[0006] The drawback of using a fixed oil return cycle is that it is impossible to obtain the actual amount of lubricating oil in the compressor, making it difficult to delay oil return when there is oil and advance oil return when there is a shortage of oil.

[0007] In addition, the oil return frequency is the compressor frequency during oil return. In the existing technology, for multi-split air conditioning systems with multiple outdoor units in parallel, due to the influence of installation, the amount of liquid returned by each outdoor unit during operation is different, and the amount of oil returned is also different, resulting in different degrees of oil shortage in the compressor. For example, in a multi-split air conditioning system with four outdoor units in parallel, the outdoor unit closest to the indoor unit usually has the largest amount of liquid returned and the largest amount of lubricating oil returned to the compressor, while the outdoor unit furthest from the indoor unit has the smallest amount of liquid returned and the smallest amount of lubricating oil returned to the compressor. In this case, if each outdoor unit maintains the same oil return frequency during oil return circulation, it may always result in the nearest outdoor unit being rich in oil and the furthest outdoor unit being poor in oil. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a multi-unit oil return control method. When multiple outdoor units are connected in parallel in a system, the oil return cycle is corrected according to the intake superheat data between each outdoor unit, thereby achieving on-demand oil return.

[0009] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0010] In a first aspect, the present invention provides a multi-split air conditioning unit oil return control method, based on a multi-split air conditioning system including at least one outdoor unit, the method comprising the following steps:

[0011] Obtain the intake superheat data of each outdoor unit during the current oil return cycle;

[0012] The oil return parameters are corrected based on the intake superheat data of each outdoor unit during the current oil return cycle.

[0013] Furthermore, obtain the intake superheat data of each outdoor unit within the current oil return cycle, including: obtaining the average value SHA of the intake superheat values ​​of all outdoor units.

[0014] Furthermore, obtaining the intake superheat data of each outdoor unit within the current oil return cycle also includes: obtaining the average value SHI of multiple sets of intake superheat values ​​collected by each outdoor unit within the current oil return cycle.

[0015] Furthermore, based on the intake superheat data of each outdoor unit during the current oil return cycle, the oil return parameters are corrected, including:

[0016] The oil return cycle of the outdoor unit is adjusted based on the average intake superheat (SHA) of all outdoor units.

[0017] Furthermore, the oil return cycle of the external engine is adjusted, and the specific adjustment formula is as follows:

[0018] TR1 = TR0 * f(SH0 / SHA)

[0019] f(SH0 / SHA)=A*SH0 / SHA, and M≤f(SH0 / SHA)≤N

[0020] Where M is the lower limit of the correction for the oil return cycle by the intake superheat;

[0021] N is the upper limit of the correction for the oil return cycle by the intake superheat;

[0022] A is the correction factor for the oil return cycle caused by intake superheat;

[0023] SH0 is the standard intake superheat.

[0024] f(SH0 / SHA) is the return oil cycle correction function;

[0025] TR1 is the corrected return oil cycle, and TR0 is the standard return oil cycle.

[0026] Furthermore, M is set to 0.5, N to 1.5, A to 1, and SH0 to 3℃.

[0027] Furthermore, based on the intake superheat data of each outdoor unit during the current oil return cycle, the oil return parameters are corrected, which also includes:

[0028] Based on the current average intake superheat SHI of outdoor unit I and the average intake superheat SHA of all outdoor units, the oil return frequency of outdoor unit I is corrected, where I = 1, 2, ..., N, and N is the total number of outdoor units.

[0029] Furthermore, based on the current average intake superheat SHI of outdoor unit I and the average intake superheat SHA of all outdoor units, the oil return frequency of outdoor unit I is corrected, including:

[0030] The current oil return frequency of outdoor unit I is corrected using the following formula:

[0031] FPI = FP0 * g(SHA / SHI)

[0032] g(SHA / SHI)=B*SHA / SHI, and M2≤g(SHA / SHI)≤N2

[0033] Wherein, FPI is the corrected oil return frequency of the current outdoor unit I;

[0034] FP0 is the standard return oil frequency;

[0035] SHI is the average intake superheat of outdoor unit I during the current oil return cycle, where I = 1, 2, ..., N, and N is the total number of outdoor units;

[0036] SHA is the average intake superheat of all outdoor units;

[0037] M2 is the lower limit of the correction for the return oil frequency based on the intake superheat.

[0038] N2 is the upper limit of the correction for the return oil frequency by the intake superheat.

[0039] B is the correction coefficient for the oil return frequency based on the intake superheat.

[0040] g(SHA / SHI) is the return oil frequency correction function.

[0041] Furthermore, M2 is set to 0.5, N2 to 1.5, and B to 1.

[0042] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0043] 1. This patent corrects the oil return cycle based on the outdoor unit intake superheat data within the oil return cycle, overcoming the problem that the oil return cycle in the prior art is inconvenient to adjust according to the actual situation. By adjusting the oil return cycle, on-demand oil return can be effectively achieved.

[0044] 2. This invention adjusts the oil return cycle based on the average suction superheat SHA. If the average suction superheat SHA > the standard suction superheat SH0, it indicates that the amount of liquid carried by the compressor suction is small during this cycle, so the oil return cycle should be shortened. The calculated oil return cycle TR1 < TR0. If the average suction superheat SHA < the standard suction superheat SH0, it indicates that the amount of liquid carried by the compressor suction is large during this cycle, so the oil return cycle can be extended. The calculated oil return cycle TR1 > TR0. This can effectively achieve on-demand oil return, delaying oil return when there is oil and advancing oil return when there is a shortage of oil.

[0045] 3. When multiple outdoor units are connected in parallel, this invention corrects the oil return frequency of each outdoor unit based on the difference in average suction superheat between the units. If the average suction superheat of outdoor unit I (SHI) is greater than that of SHA, it indicates that this unit is always in a state of low oil return. Therefore, during the oil return cycle, FPI is calculated to be less than FP0, and the oil return frequency of this unit can be lower to ensure that the oil discharge of this unit is less during the oil return cycle. If the average suction superheat of outdoor unit I (SHI) is less than that of SHA, it indicates that this unit is always in a state of high oil return. Therefore, during the oil return cycle, FPI is calculated to be greater than FP0, and the oil return frequency of this unit can be higher to ensure that the oil discharge of this unit is greater during the oil return cycle. More lubricating oil can be distributed to other outdoor units, effectively achieving on-demand oil distribution and avoiding the situation where the nearest outdoor unit is rich in oil and the farthest outdoor unit is poor in oil. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the oil return cycle of a multi-split air conditioning unit;

[0047] Figure 2 This is a schematic diagram of oil return calculation for multi-split air conditioning units. Detailed Implementation

[0048] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0049] Example 1:

[0050] This implementation provides a method comprising the following steps:

[0051] Step 1: When the multi-split unit returns oil, set the initial "TR0 Standard Oil Return Cycle". TR0 is an empirical value obtained by the developers based on the standard intake superheat SH0.

[0052] In actual operation of multi-split air conditioners, the actual average intake superheat (SHA) of the outdoor unit deviates from the standard intake superheat (SH0), thus altering its oil return requirement. Based on this, this patent proposes adjusting the oil return cycle according to the average intake superheat (SHA) of the outdoor unit within the oil return cycle, thereby achieving on-demand oil return.

[0053] Step 2: ① A multi-split air conditioning system consists of N outdoor units, where N ≥ 1; ② When there are multiple outdoor units in the system, due to differences in installation location, the suction superheat of each outdoor unit will vary during operation, such as SH1, SH2, ..., SHI, I = 1, 2, ..., N, which represent the average suction superheat of outdoor units 1, 2, ..., I during the oil return cycle timing time, respectively. Since the values ​​of SH1, SH2, ..., SHI are different, the oil return requirements of each outdoor unit are different; ③ When the multi-split air conditioning system returns oil, the developers will initially determine an initial standard oil return frequency FP0 based on the standard suction superheat SH0; ④ This patent proposes that, for multiple outdoor units connected in parallel within the system, the oil return frequency of each outdoor unit is corrected according to the difference in the average suction superheat (SH1, SH2, ..., SHN) between the outdoor units, thereby achieving on-demand oil distribution among the outdoor units when multiple outdoor units are connected in parallel.

[0054] The specific calculation methods for average intake superheat include:

[0055] ① A multi-split air conditioning system consists of N outdoor units, where N ≥ 1;

[0056] ② During the operation of each outdoor unit, data is generated in real time, such as recording data once per second. The data includes the intake superheat value, which is measured by sensors on the outdoor unit; each oil return cycle consists of a relatively long time, such as... Figure 1 As shown, there will be multiple sets of data in each oil return cycle. For example, if the oil return occurs once every 6 hours, that is, the oil return cycle is 6 hours. Then, 6*3600=21600 sets of intake superheat data will be recorded in the oil return cycle.

[0057] ③ "SHI: Average value of intake superheat during the current oil return cycle of outdoor unit I", represents the average value of intake superheat of outdoor unit I within 21,600 sets during the oil return cycle;

[0058] ④ As explained in ①, the multi-split system consists of N outdoor units, where N≥1. The average suction superheat of the outdoor unit SHA represents the average suction superheat of N*21600 groups within the oil return cycle, where N is the number of outdoor units.

[0059] Oil return cycle TR1 = TR0 * f(SH0 / SHA)

[0060] f(SH0 / SHA)=A*SH0 / SHA, and M≤f(SH0 / SHA)≤N

[0061] M: Lower limit of the correction for the oil return cycle based on the intake superheat; typically M can be set to 0.5;

[0062] N: Upper limit of the correction for the oil return cycle due to intake superheat; M can usually be taken as 1.5;

[0063] A: Correction coefficient for intake superheat on oil return cycle; M can usually be taken as 1;

[0064] SH0: Standard intake superheat, typically taken as 3°C;

[0065] TR1 is the current return oil cycle, and TR0 is the standard return oil cycle;

[0066] SHA: Average intake superheat, which is the average intake superheat during the current oil return cycle. If there are multiple outdoor units in a system, the average intake superheat of each outdoor unit is taken.

[0067] According to the formula: Return oil cycle TR1=TR0*f(SH0 / SHA), it can be seen that:

[0068] When the average suction superheat SHA > standard suction superheat SH0, it indicates that the amount of liquid carried by the compressor suction is small in this cycle. Therefore, the oil return cycle should be shortened. The calculated oil return cycle TR1 < TR0.

[0069] When the average suction superheat SHA < standard suction superheat SH0, it indicates that the amount of liquid carried by the compressor suction is large during this cycle. Therefore, the oil return cycle can be extended, and the calculated oil return cycle TR1 > TR0.

[0070] Outdoor unit I oil return frequency FPI=FP0*g(SHA / SHI)

[0071] g(SHA / SHI)=B*SHA / SHI, and M2≤g(SHA / SHI)≤N2

[0072] FP0: Standard return oil frequency;

[0073] M2: Lower limit for correction of intake superheat to return oil frequency; typically M2 can be set to 0.5;

[0074] N2: Upper limit of the correction for intake superheat to return oil frequency; N2 is usually set to 1.5;

[0075] B: Correction coefficient for intake superheat on oil return frequency; usually taken as 1.

[0076] SHI: Average intake superheat during the current oil return cycle time of outdoor unit I;

[0077] According to the formula: Outdoor unit I oil return frequency FPI=FP0*g(SHA / SHI), it can be seen that:

[0078] The average intake superheat of outdoor unit I, SHI, is greater than the average intake superheat of SHA. This indicates that the outdoor unit is always in a state of low oil return. Therefore, during the oil return circulation, the calculated FPI is less than FP0. The oil return frequency of the outdoor unit can be lower to ensure that the oil discharge of the outdoor unit is low during the oil return circulation.

[0079] If the average intake superheat of outdoor unit I is SHI < SHA, it indicates that this outdoor unit is always in a state of high liquid return. Therefore, during the oil return circulation, the calculated FPI > FP0 indicates that the oil return frequency of this outdoor unit can be higher to ensure that the oil discharge of this outdoor unit is greater during the oil return circulation, so that more lubricating oil can be used for other outdoor units.

[0080] Definitions:

[0081] Superheat: The actual temperature is a few degrees higher than the saturation temperature corresponding to the actual pressure. Generally, at the evaporator outlet and compressor discharge port, the actual temperature of the working fluid is higher than the saturation temperature corresponding to the actual pressure. This is where superheat comes in, including suction superheat and discharge superheat.

[0082] The oil return cycle refers to the time interval between two oil return operations.

[0083] Standard return oil frequency and standard return oil cycle can be obtained from product manufacturer parameters or estimated through experience.

[0084] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0085] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0086] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0087] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0088] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling oil return in a multi-split air conditioning unit, characterized in that, Includes the following steps: Obtain the intake superheat data of each outdoor unit during the current oil return cycle; Based on the intake superheat data of each outdoor unit during the current oil return cycle, the oil return parameters are corrected. Obtain the intake superheat data of each outdoor unit within the current oil return cycle, including: obtaining the average value SHA of the intake superheat of all outdoor units; Based on the intake superheat data of each outdoor unit during the current oil return cycle, the oil return parameters are corrected, including: The oil return cycle of the outdoor unit is adjusted based on the average intake superheat (SHA) of all outdoor units.

2. The multi-unit oil return control method according to claim 1, characterized in that, The method for obtaining intake superheat data of each outdoor unit within the current oil return cycle also includes obtaining the average value SHI of multiple intake superheat values ​​collected by each outdoor unit within the current oil return cycle.

3. The multi-unit oil return control method according to claim 1, characterized in that, The oil return cycle of the external engine is adjusted using the following formula: TR1 = TR0 * f(SH0 / SHA) f(SH0 / SHA)=A*SH0 / SHA, and M≤f(SH0 / SHA)≤N Where M is the lower limit of the correction for the oil return cycle by the intake superheat; N is the upper limit of the correction for the oil return cycle by the intake superheat; A is the correction factor for the oil return cycle caused by intake superheat; SH0 is the standard intake superheat. f(SH0 / SHA) is the return oil cycle correction function; TR1 is the corrected return oil cycle, and TR0 is the standard return oil cycle.

4. The multi-unit oil return control method according to claim 3, characterized in that, M is set to 0.5, N to 1.5, A to 1, and SH0 to 3℃.

5. The multi-unit oil return control method according to claim 3, characterized in that, Based on the intake superheat data of each outdoor unit during the current oil return cycle, the oil return parameters are corrected, including: Based on the current average intake superheat SHI of outdoor unit I and the average intake superheat SHA of all outdoor units, the oil return frequency of outdoor unit I is corrected, where I = 1, 2, ..., N, and N is the total number of outdoor units.

6. The multi-unit oil return control method according to claim 5, characterized in that, Based on the current average intake superheat SHI of outdoor unit I and the average intake superheat SHA of all outdoor units, the oil return frequency of outdoor unit I is corrected using the following formula: FPI = FP0 * g(SHA / SHI); g(SHA / SHI)=B*SHA / SHI, and M2≤g(SHA / SHI)≤N2; Wherein, FPI is the corrected oil return frequency of the current outdoor unit I; FP0 is the standard return oil frequency; SHI is the average intake superheat of outdoor unit I during the current oil return cycle, where I = 1, 2, ..., N, and N is the total number of outdoor units; SHA is the average intake superheat of all outdoor units; M2 is the lower limit of the correction for the return oil frequency based on the intake superheat. N2 is the upper limit of the correction for the return oil frequency by the intake superheat. B is the correction coefficient for the oil return frequency based on the intake superheat. g(SHA / SHI) is the return oil frequency correction function.

7. The multi-unit oil return control method according to claim 6, characterized in that, M2 is set to 0.5, N2 to 1.5, and B to 1.

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