Control method for reducing pipeline stress during starting and stopping of multi-split air conditioner

Abstract

The invention provides a control method for reducing pipeline stress during startup and shutdown of a multi-split air conditioner, which comprises the following steps of: in the startup stage of the air conditioner, controlling the frequency of a compressor to be directly increased from 0 to 20Hz, when the frequency reaches 20Hz, reducing the frequency to 15Hz, opening an oil return electromagnetic valve and a load release electromagnetic valve, setting a supercooling electronic expansion valve as a first step number, and setting a second step number as a third step number; after the compressor operates for 60 seconds at the frequency of 15 Hz, the oil return electromagnetic valve and the load release electromagnetic valve are closed; and in the shutdown stage of the air conditioner, the compressor is controlled to be subjected to frequency reduction at the first frequency, the oil return electromagnetic valve and the load release electromagnetic valve are opened, and when the frequency of the compressor is reduced to 15 Hz and lasts for 30 s, or the high pressure HP-low pressure LP is smaller than 0.5 MPa, the oil return electromagnetic valve and the load release electromagnetic valve are closed. High and low pressure can be quickly balanced, vibration during starting and stopping of the press is reduced, pipeline stress is reduced, the oil throwing amount of the press during starting and stopping of the press is reduced, and the compressor is prevented from being damaged by return liquid.

Description

Technical Field

[0001] This invention relates to the field of multi-split air conditioning technology, and in particular to a control method for reducing pipeline stress during the start-up and shutdown of multi-split air conditioning systems. Background Technology

[0002] During the start-up phase of an air conditioner, when the system's high and low pressures are unbalanced, a large current is input to complete the startup process. This sudden influx of current can cause significant compressor vibration and increased pipe stress, potentially leading to pipe rupture. Similarly, when the air conditioner shuts down, especially during high-temperature cooling or ultra-low-temperature heating, the large pressure difference between the high and low pressures causes a sudden stop. The compressor stops, and the refrigerant on the low-pressure side, due to inertia, impacts the compressor, resulting in increased compressor vibration and greater pipe stress, also potentially leading to pipe rupture. Summary of the Invention

[0003] This invention provides a control method for reducing pipeline stress during the start-up and shutdown of multi-split air conditioners, solving the problem that existing multi-split air conditioners directly control the start-up and shutdown phases without pressure equalization control, which may lead to a sudden increase in pipeline pressure and rupture.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a control method for reducing pipeline stress during the start-up and shutdown of a multi-split air conditioner. The method involves installing an oil return solenoid valve between the oil separator and the compressor's suction port of the multi-split air conditioner; installing a load relief solenoid valve between the pipeline connecting the compressor's suction port and the gas-liquid separator, and between the pipeline connecting the one-way valve and the four-way valve; and installing a subcooling electronic expansion valve between the fourth port and the first port of the auxiliary subcooling heat exchanger. During the air conditioner's start-up phase, the compressor frequency is controlled to increase directly from 0 to 20Hz. Once 20Hz is reached, it is then reduced to 15Hz. The oil return solenoid valve and the load relief solenoid valve are opened, and the subcooling electronic expansion valve is set to the first step. After the compressor runs at 15Hz for 60 seconds, the oil return solenoid valve and the load relief solenoid valve are closed. During the air conditioner's shutdown phase, the compressor is controlled to reduce its frequency to the first frequency. The oil return solenoid valve and the load relief solenoid valve are opened. When the compressor frequency drops to 15Hz and remains there for 30 seconds, or when the high pressure (HP) minus the low pressure (LP) is less than 0.5MPa, the oil return solenoid valve and the load relief solenoid valve are closed.

[0005] Preferably, the first frequency is 2Hz / s.

[0006] Preferably, the start-up phase requires the compressor to be shut down for 3 minutes to equalize the pressure before the operation of controlling the compressor frequency to be directly increased from 0 to 20Hz can be performed.

[0007] Preferably, the return oil solenoid valve is connected in series with the first capillary tube and then in parallel with the second capillary tube.

[0008] Preferably, the diameter of the return oil solenoid valve is 1.2-1.6 mm.

[0009] Preferably, the diameter of the unloading solenoid valve is 1.8-2.4 mm.

[0010] Preferably, the number of steps in the first step is 40-80.

[0011] Compared with the prior art, the advantages and positive effects of the present invention are: it can quickly balance high and low pressure, reduce vibration during press start-up and shutdown, and reduce pipeline stress; it can reduce the amount of oil thrown out by the press during start-up and shutdown, and avoid the problem of press unreliability caused by backflow. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a multi-split air conditioning system according to an embodiment of the present invention.

[0013] The image is labeled as follows: 1. Compressor; 2. Oil separator; 3. Gas-liquid separator; 4. Check valve; 5. Four-way valve; 6. Auxiliary subcooling heat exchanger; 7. First capillary tube; 8. Second capillary tube; 9. Oil return solenoid valve SV6; 10. Unloading valve SV8; 11. Subcooling electronic expansion valve EEVSC. Detailed Implementation

[0014] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below through embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0015] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0016] like Figure 1As shown, this embodiment provides a control method for reducing pipeline stress during the start-up and shutdown of a multi-split air conditioner. The method involves installing an oil return solenoid valve SV6 between the oil separator 2 and the suction port of the compressor 1; installing a load relief solenoid valve SV8 between the pipeline connecting the compressor 1 suction port to the gas-liquid separator 3 and the pipeline connecting the one-way valve 4 and the four-way valve 5; and installing a subcooling electronic expansion valve EEVSC between the fourth port and the first port of the auxiliary subcooling heat exchanger 6. During the air conditioner start-up phase, the compressor frequency is controlled to increase directly from 0. Increase the frequency to 20Hz, and then reduce it to 15Hz. Open the oil return solenoid valve and the load relief solenoid valve, and set the subcooled electronic expansion valve to the first step. After the compressor runs at 15Hz for 60 seconds, close the oil return solenoid valve and the load relief solenoid valve. During the air conditioner shutdown phase, control the compressor to reduce its frequency to the first frequency, open the oil return solenoid valve and the load relief solenoid valve, and close the oil return solenoid valve and the load relief solenoid valve when the compressor frequency drops to 15Hz and lasts for 30 seconds, or when the high pressure HP - low pressure LP is less than 0.5MPa.

[0017] In a preferred embodiment of this example, the first frequency is 2Hz / s.

[0018] As a preferred embodiment of this example, the compressor frequency can only be directly increased from 0 to 20Hz after the compressor has been shut down for 3 minutes during the start-up phase.

[0019] In a preferred embodiment of this invention, the return oil solenoid valve is connected in series with the first capillary tube 7 and then in parallel with the second capillary tube 8.

[0020] In a preferred embodiment of this invention, the diameter of the return solenoid valve is 1.2-1.6 mm.

[0021] In a preferred embodiment of this example, the diameter of the unloading solenoid valve is 1.8-2.4 mm.

[0022] In a preferred embodiment of this example, the number of steps in the first step is 40-80.

[0023] To balance the high and low voltage of the system, it is mainly achieved through control. Figure 1The compressor control is achieved through the return oil solenoid valve SV6, unloading valve SV8, and subcooled electronic expansion valve EEVSC. The compressor control is divided into two phases: startup and shutdown. During startup, the compressor's inverter module sets the hard-start frequency to 20Hz, then reduces it to 15Hz. This ensures a low starting input current and minimal compressor vibration. Additionally, the low compressor frequency during startup results in a small high-low pressure difference, further reducing compressor vibration and ensuring low pipeline vibration and stress. During shutdown, the compressor does not immediately reduce its frequency to 0Hz. Instead, it reduces the frequency at a rate of 2Hz / s, ensuring the high-low pressure difference is less than 0.5MPa or the compressor frequency reaches the minimum frequency of 15Hz and remains there for 30 seconds before stopping. This effectively prevents the refrigerant on the low-pressure side from inertially impacting the compressor, increasing compressor vibration, and thus preventing excessive pipeline vibration stress and potential pipeline damage. The oil return solenoid valve SV6 has three functions during startup and shutdown: First, it quickly balances high and low pressure, ensuring minimal or no pressure difference during compressor startup and shutdown, resulting in less stress and friction on moving parts, thus reducing vibration and pipeline stress. Second, given the high temperature on the compressor's discharge side, if the refrigerant returning from the suction side is liquid or a gas-liquid mixture, mixing with the high-temperature refrigerant on the discharge side will cause the liquid refrigerant to evaporate into a gaseous state, preventing the compressor from directly compressing the liquid refrigerant and causing it to fail. Third, the compressor oil stored at the bottom of the oil separator will go directly to the compressor's suction side, lubricating the compressor's moving parts and improving compressor reliability. The unloading solenoid valve SV8 connects the high-pressure side of the refrigerant system to the low-pressure side of the system, and its function during startup and shutdown is the same as that of the oil return solenoid valve SV6. The main function of the subcooling electronic expansion valve (EEVSC) is for subcooling applications, increasing the subcooling degree of the refrigerant and thus extending the length of the connecting piping. This electronic expansion valve is connected between the medium pressure and low pressure of the refrigerant system. During the startup phase, the valve opening is set between 40 and 80 steps. The main purpose is to reduce the pressure difference between the high and low pressures during system startup, thereby reducing compressor vibration and minimizing piping stress. Additionally, setting the opening to 40-80 steps is to prevent system backflow.

[0024] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A control method for reducing pipeline stress during the start-up and shutdown of a multi-split air conditioner, the method comprising installing an oil return solenoid valve between the oil separator and the compressor suction port of the multi-split air conditioner, installing a load relief solenoid valve between the pipeline connecting the compressor suction port and the gas-liquid separator and the pipeline connecting the one-way valve and the four-way valve, and installing a subcooling electronic expansion valve between the fourth port and the first port of the auxiliary subcooling heat exchanger, characterized in that: During the air conditioner startup phase, the compressor frequency is controlled to increase directly from 0 to 20Hz. Once 20Hz is reached, it is reduced to 15Hz. The oil return solenoid valve and the load relief solenoid valve are opened, and the subcooling electronic expansion valve is set to the first step. After the compressor runs at 15Hz for 60 seconds, the oil return solenoid valve and the load relief solenoid valve are closed. During the air conditioner shutdown phase, the compressor is controlled to reduce its frequency to the first frequency. The oil return solenoid valve and the load relief solenoid valve are opened. When the compressor frequency drops to 15Hz and remains there for 30 seconds, or when the high pressure (HP) - low pressure (LP) is less than 0.5MPa, the oil return solenoid valve and the load relief solenoid valve are closed.

2. The control method for reducing pipeline stress during start-up and shutdown of a multi-split air conditioner according to claim 1, characterized in that: The first frequency is 2Hz / s.

3. The control method for reducing pipeline stress during start-up and shutdown of a multi-split air conditioner according to claim 1, characterized in that: The startup phase requires the compressor to be shut down for 3 minutes to equalize the pressure before the operation of directly increasing the compressor frequency from 0 to 20Hz can be performed.

4. The control method for reducing pipeline stress during start-up and shutdown of a multi-split air conditioner according to claim 1, characterized in that: The return oil solenoid valve is connected in series with the first capillary tube and then in parallel with the second capillary tube.

5. The control method for reducing pipeline stress during start-up and shutdown of a multi-split air conditioner according to claim 4, characterized in that: The diameter of the return oil solenoid valve is 1.2-1.6mm.

6. The control method for reducing pipeline stress during start-up and shutdown of a multi-split air conditioner according to claim 1, characterized in that: The diameter of the unloading solenoid valve is 1.8-2.4mm.

7. The control method for reducing pipeline stress during start-up and shutdown of a multi-split air conditioner according to claim 1, characterized in that: The first step consists of 40-80 steps.

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