A heating ventilation system oil return control method, device, equipment and medium

Abstract

This invention discloses a method, apparatus, equipment, and medium for controlling oil return in HVAC systems, relating to the field of HVAC technology. The method includes: determining that the HVAC system meets preset oil return trigger conditions and enters an oil return mode; determining the exhaust superheat at the start of the oil return mode; determining the current operating condition type of the HVAC system based on the exhaust superheat; determining oil return control parameters based on the operating condition type, and executing an oil return operation based on the oil return control parameters until a preset oil return completion condition is met, after which the oil return mode is exited. By differentiating different operating conditions of the HVAC system and matching appropriate oil return control parameters to different conditions, targeted oil return operations are formulated and executed, ensuring that the oil return strategy is adapted to the actual superheat conditions of the system. While ensuring effective flushing of accumulated oil in the pipes, improper oil return operations are avoided from affecting the compressor's operating status, ultimately ensuring the reliable operation of the HVAC system compressor.

Description

Technical Field

[0001] This invention relates to the field of heating, ventilation and air conditioning (HVAC) technology, and specifically to a method, apparatus, equipment, and medium for controlling oil return in HVAC systems. Background Technology

[0002] In HVAC systems, the normal operation of the compressor relies on the lubrication of refrigerant oil. Refrigerant oil prevents hard friction between moving parts, and maintaining a safe oil level in the compressor is a key aspect of system control. Existing HVAC systems have a relatively simple oil return method. After activating the oil return mode, the refrigerant flow is increased directly by raising the compressor frequency and opening system valves, relying on the refrigerant flow to carry the accumulated refrigerant oil in the pipeline back to the compressor.

[0003] However, under low-load conditions such as high-temperature heating and low-temperature cooling, the system often operates at a low frequency, resulting in a decrease in compressor discharge superheat. In this case, the compressor oil discharge rate is relatively high. If the oil return is directly increased in the current way, a large amount of refrigerant oil will be discharged, which can easily lead to insufficient oil return or excessive oil return, resulting in compressor oil shortage. Summary of the Invention

[0004] The main objective of this invention is to provide a method, device, equipment, and medium for oil return control in HVAC systems. To address the problems of incomplete oil return, compressor oil leakage, or oil shortage caused by the single strategy used in traditional HVAC system oil return control, which fails to adjust the oil return method based on exhaust superheat characteristics, this invention achieves precise oil return control based on operating conditions. After activating the oil return mode when preset trigger conditions are met, the invention differentiates different operating conditions of the HVAC system based on the comparison between exhaust superheat and a preset critical value, combined with the duration of the state. Appropriate oil return control parameters are then matched to different operating conditions, allowing for targeted oil return operations to be formulated and executed. This ensures that the oil return strategy is adapted to the actual superheat conditions of the system. While ensuring effective flushing of accumulated oil in the pipes, improper oil return operations are avoided from affecting the compressor's operating state, ultimately guaranteeing the reliable operation of the HVAC system compressor and improving the adaptability and effectiveness of oil return control.

[0005] To achieve the above objectives, the embodiments of this application provide the following technical solutions: According to a first aspect of the embodiments of this application, a method for controlling oil return in a heating, ventilation, and air conditioning (HVAC) system is provided, the method comprising: Once the HVAC system meets the preset oil return trigger conditions, it enters the oil return mode. Determine the exhaust superheat at the moment the return oil mode is activated; The current operating condition type of the HVAC system is determined based on the exhaust superheat. The return oil control parameters are determined based on the operating condition type, and the return oil operation is performed based on the return oil control parameters until the preset return oil completion condition is met and then the return oil mode is exited.

[0006] Optionally, determining the current operating condition type of the HVAC system based on the exhaust superheat includes: Based on the fact that the exhaust superheat is less than or equal to a preset critical superheat value, and the duration of the state where the exhaust superheat is less than or equal to the preset critical superheat value reaches a preset duration, the operating condition type of the HVAC system is determined to be the first superheat condition. The operating condition type of the HVAC system is determined to be the second superheat condition based on the exhaust superheat being less than or equal to the preset critical superheat value and the duration of the state not reaching the preset duration, or based on the exhaust superheat being greater than the preset critical superheat value. The exhaust superheat corresponding to the first superheat condition is less than or equal to the preset critical superheat value, the exhaust superheat corresponding to the second superheat condition is greater than the preset critical superheat value, and the exhaust superheat under the second superheat condition is greater than the exhaust superheat under the first superheat condition.

[0007] Optionally, when the operating condition type is a high superheat condition, the return oil control parameters are determined based on the operating condition type, and the return oil operation is performed based on the return oil control parameters, including: Obtain the equipment hardware parameters of the HVAC system, wherein the equipment hardware parameters are the hardware parameters that affect the oil return effect under high superheat conditions; The first basic requirement for system oil return is to ensure that the accumulated refrigerant oil in the pipeline is effectively returned to the compressor. Based on the hardware parameters of the equipment, the minimum effective refrigerant return flow rate that meets the first basic requirement for system oil return is determined. The first target oil return frequency and the first target oil return time are calculated based on the minimum effective return flow rate of the first refrigerant; the first target oil return time is used to define the preset oil return completion conditions. Determine the currently oil-accumulating component based on the current operating mode of the HVAC system; Adjust the expansion valve corresponding to the currently oil-accumulating component to a preset increased opening range, and control the compressor to operate at the first target oil return frequency.

[0008] Optionally, when the operating condition type is a low superheat condition, determining the oil return control parameters based on the operating condition type and performing the oil return operation based on the oil return control parameters includes: Obtain the fluid hardware parameters of the HVAC system, wherein the fluid hardware parameters are the hardware parameters that affect the oil return effect under low superheat conditions; The second basic requirement for oil return in the system is to effectively return the accumulated refrigerant oil in the pipeline to the compressor while suppressing the compressor's oil discharge. The minimum effective return flow rate of the second refrigerant that meets the second basic requirement for oil return in the system is determined based on the fluid hardware parameters. The second target oil return frequency and the second target oil return time are calculated based on the minimum effective return flow rate of the second refrigerant; the second target oil return time is used to define the preset oil return completion condition; the second target oil return time is greater than the first target oil return time. The compressor is controlled to operate at the second target oil return frequency, wherein the second target oil return frequency is less than the first target oil return frequency.

[0009] Optionally, the oil return mode is exited after the preset oil return completion conditions are met, including: The compressor's first cumulative operating time at the first target oil return frequency is statistically analyzed in real time. Based on the first cumulative operating time reaching the first target oil return time, it is determined that the preset oil return completion condition has been met; or... The second cumulative running time of the compressor running at the second target oil return frequency is counted in real time. Based on the second cumulative running time reaching the second target oil return time, it is determined that the preset oil return completion condition is met. Based on meeting the preset oil return completion conditions, the HVAC system components are controlled to return to their operating state before entering the oil return mode, so as to exit the oil return mode.

[0010] Optionally, the exhaust superheat at the moment of oil return mode activation is determined, including: Collect the compressor's exhaust temperature and the high-pressure side pressure of the HVAC system; The high-pressure saturation temperature is obtained based on the high-pressure side pressure conversion. The difference between the exhaust temperature and the high-pressure saturation temperature is calculated as the exhaust superheat.

[0011] Optionally, the HVAC system is determined to meet preset return oil trigger conditions and enter the return oil mode, including: Real-time monitoring of the cumulative operating time of the HVAC system, and real-time calculation of the HVAC system's oil return and air venting volume; If the cumulative operating time of the HVAC system reaches a preset periodic oil return interval, then the HVAC system is determined to meet the preset oil return trigger condition and enters the oil return mode; and / or, If the return oil and exhaust volume of the HVAC system reaches the preset minimum return oil and exhaust volume, then the HVAC system is determined to meet the preset return oil trigger condition and enters the return oil mode.

[0012] According to a second aspect of the embodiments of this application, a heating, ventilation, air conditioning (HVAC) system oil return control device is provided, the device comprising: The oil return mode determination module is used to determine when the HVAC system meets the preset oil return trigger conditions and enters the oil return mode; The exhaust superheat module is used to determine the exhaust superheat at the start of the oil return mode. The operating condition determination module is used to determine the current operating condition type of the HVAC system based on the exhaust superheat. The oil return control module is used to determine the oil return control parameters based on the operating condition type, and to perform the oil return operation based on the oil return control parameters until the preset oil return completion condition is met and then exit the oil return mode.

[0013] According to a third aspect of the present application, an electronic device is provided, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method described in the first aspect above.

[0014] According to a fourth aspect of the embodiments of this application, a computer-readable storage medium is provided having computer-readable instructions stored thereon, the computer-readable instructions being executable by a processor to implement the method described in the first aspect above.

[0015] In summary, this application provides a method, apparatus, device, and medium for controlling oil return in a heating, ventilation, and air (HVAC) system. The method involves determining when the HVAC system meets a preset oil return trigger condition and entering an oil return mode; determining the exhaust superheat at the start of the oil return mode; determining the current operating condition type of the HVAC system based on the exhaust superheat; determining oil return control parameters based on the operating condition type; and executing oil return operations based on these parameters until a preset oil return completion condition is met, at which point the oil return mode is exited. This addresses the problem of traditional HVAC system oil return control using a single strategy that fails to adjust the oil return method according to the exhaust superheat characteristics, leading to incomplete oil return, compressor oil discharge, or oil shortage. The method achieves precise oil return control based on operating conditions. After starting the oil return mode when the preset trigger condition is met, the method uses the comparison between the exhaust superheat and a preset critical value, combined with the duration of the state, to distinguish different operating conditions of the HVAC system. Adaptive oil return control parameters are matched for different operating conditions, thereby formulating and executing targeted oil return operations, ensuring that the oil return strategy is adapted to the actual superheat conditions of the system. While ensuring effective flushing of oil accumulation in the pipeline, it is crucial to avoid improper oil return operations that could affect the compressor's operating status, ultimately ensuring the reliable operation of the HVAC system compressor and improving the adaptability and effectiveness of oil return control. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0018] Figure 1 A flowchart of a method for controlling oil return in a heating, ventilation, and air conditioning system is provided in an embodiment of this application; Figure 2 This is a schematic diagram of the cooling mode of a heating, ventilation, and air conditioning system provided in an embodiment of this application; Figure 3 This is a schematic diagram of the heating mode of the HVAC system provided in the embodiments of this application; Figure 4 This is a schematic diagram of the adaptive oil return control method provided in the embodiments of this application; Figure 5 A schematic diagram of the HVAC system oil return control device provided in the embodiments of this application; Figure 6 This paper shows a structural diagram of an electronic device provided in an embodiment of this application; Figure 7 A diagram of a computer-readable storage medium provided in an embodiment of this application is shown.

[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0022] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0023] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0025] Figure 1 This application illustrates a method for controlling oil return in a heating, ventilation, and air conditioning (HVAC) system, comprising: Step 101: Determine that the HVAC system meets the preset oil return trigger conditions and enter the oil return mode; Step 102: Determine the exhaust superheat at the moment of starting the return oil mode; Step 103: Determine the current operating condition type of the HVAC system based on the exhaust superheat. Step 104: Determine the return oil control parameters based on the operating condition type, and perform the return oil operation based on the return oil control parameters until the preset return oil completion condition is met, and then exit the return oil mode.

[0026] The HVAC system oil return control method provided in this application addresses the technical problems of traditional HVAC system oil return control, which uses a single strategy and fails to adapt the oil return operation to the actual operating conditions of the system. This often results in incomplete oil return, compressor oil leakage or insufficient oil, thus affecting the reliability of compressor operation. The method achieves precise oil return control for HVAC systems, ensuring the compressor maintains a safe oil level while improving the adaptability and effectiveness of oil return control. First, a preset oil return trigger condition is used to determine whether to activate the oil return mode, avoiding meaningless oil return operations that could interfere with normal system operation. After the oil return mode is activated, the exhaust superheat is used as a key indicator to determine the system's operating condition. This parameter directly reflects the compressor's exhaust state and the system's refrigerant circulation characteristics, making the condition determination result more consistent with the actual operating conditions of the HVAC system. Based on the operating condition type determined by the exhaust superheat, appropriate return oil control parameters are matched for different operating conditions and targeted return oil operations are performed. This breaks the limitations of traditional single return oil parameters, making the return oil strategy highly compatible with the current operating state of the system, and effectively avoiding the problems of insufficient or excessive return oil under different operating conditions when the same return oil operation is used.

[0027] In one possible implementation, in step 101, determining that the HVAC system meets a preset oil return trigger condition and enters the oil return mode includes: real-time detection of the cumulative operating time of the HVAC system and real-time calculation of the oil return and exhaust volume of the HVAC system; determining that the HVAC system meets the preset oil return trigger condition and enters the oil return mode based on the cumulative operating time of the HVAC system reaching a preset periodic oil return interval; and / or determining that the HVAC system meets the preset oil return trigger condition and enters the oil return mode based on the oil return and exhaust volume of the HVAC system reaching a preset minimum oil return and exhaust volume.

[0028] This implementation details the logic for determining the HVAC system oil return trigger condition in step 101. It uses a dual-dimensional approach of cumulative runtime and oil return discharge volume as the trigger conditions. Meeting either condition initiates the oil return mode, balancing the periodicity of HVAC system operation with the real-time nature of actual operation. The cumulative runtime dimension is based on the characteristic that oil accumulates gradually in HVAC system pipes over time. By presetting a periodic oil return interval, it achieves timed preventative oil return, avoiding excessive oil accumulation that could affect the compressor's normal operation. The oil return discharge volume dimension aligns with the actual operating characteristics of the HVAC system. It directly reflects the system's current oil return capacity. When the oil return discharge volume reaches the preset minimum, it indicates that the system's own oil return capacity is insufficient to meet the oil return demand. In this case, timely triggering of the oil return mode enables precise, on-demand oil return, preventing oil accumulation due to insufficient oil-carrying capacity.

[0029] This implementation uses real-time detection of cumulative runtime and real-time calculation of return oil discharge volume, enabling dynamic and accurate acquisition of HVAC system operating parameters. This ensures the real-time nature and accuracy of return oil trigger condition determination, avoiding untimely return oil initiation due to parameter acquisition delays or false triggering due to parameter judgment deviations. Simultaneously, the dual-dimensional trigger conditions employ an "AND / OR" logic determination method, adaptable to different operating scenarios of the HVAC system. Whether the system operates at low load for extended periods, resulting in insufficient oil carrying capacity, or the system operates at normal high load for a preset period, the return oil mode can be precisely triggered. This lays a solid foundation for the accurate implementation of the entire return oil control process, ensuring timely handling of oil accumulation in the pipeline from the initial stage of return oil control, preventing the cumulative oil accumulation problem from affecting the operational stability of the compressor and the entire HVAC system.

[0030] In one possible implementation, in step 102, determining the exhaust superheat at the start of the oil return mode includes: collecting the compressor's exhaust temperature and the high-pressure side pressure of the HVAC system; calculating the high-pressure saturation temperature based on the high-pressure side pressure; and calculating the difference between the exhaust temperature and the high-pressure saturation temperature as the exhaust superheat.

[0031] This implementation details the method for determining the exhaust superheat at the start of the oil return mode in step 102. It uses the compressor's exhaust temperature and the system's high-pressure side pressure as the basis for calculation. Both parameters can be directly obtained from the temperature and pressure detection components configured in the HVAC system, eliminating the need for additional hardware and reducing the actual application cost of the solution. After obtaining the basic detection parameters, the high-pressure saturation temperature is calculated based on the high-pressure side pressure. This calculation process relies on the refrigerant's thermal properties and accurately reflects the refrigerant's saturation temperature benchmark under the current operating state of the HVAC system. This provides an accurate and unified reference value for calculating the exhaust superheat, avoiding distortion of the calculation results due to benchmark deviations.

[0032] The exhaust superheat is determined by calculating the difference between the exhaust temperature and the high-pressure saturation temperature. This calculation logic is the standard method in this field for defining refrigerant superheat. The calculation process is simple and the results are highly quantifiable, directly reflecting the degree to which the compressor exhaust state deviates from the refrigerant saturation state, thus accurately reflecting the system's refrigerant circulation efficiency and the compressor's operating conditions. This method achieves accurate and repeatable acquisition of exhaust superheat at the start of the oil return mode, avoiding numerical deviations caused by non-standard parameter acquisition methods, and providing a reliable parameter acquisition foundation for the implementation of the entire oil return control method.

[0033] In one possible implementation, step 103, determining the current operating condition type of the HVAC system based on the exhaust superheat, includes: Based on the fact that the exhaust superheat is less than or equal to a preset critical superheat value, and the duration of the state where the exhaust superheat is less than or equal to the preset critical superheat value reaches a preset duration, the operating condition type of the HVAC system is determined to be the first superheat condition; the duration of the state is the continuous duration of the state where the exhaust superheat is less than or equal to the preset critical superheat value. The operating condition type of the HVAC system is determined to be the second superheat condition based on the exhaust superheat being less than or equal to the preset critical superheat value and the duration of the state not reaching the preset duration, or based on the exhaust superheat being greater than the preset critical superheat value. The exhaust superheat corresponding to the first superheat condition is less than or equal to the preset critical superheat value, the exhaust superheat corresponding to the second superheat condition is greater than the preset critical superheat value, and the exhaust superheat under the second superheat condition is greater than the exhaust superheat under the first superheat condition.

[0034] This embodiment refines the method for determining the operating condition type of the HVAC system in step 103. It first clarifies the criteria for determining the first superheat condition, requiring that the exhaust superheat be less than or equal to a preset critical superheat value, and that the duration of this state be maintained for a preset duration. Furthermore, the duration of this state is specifically defined as the continuous maintenance duration of exhaust superheat ≤ preset critical superheat value. This effectively eliminates the interference of instantaneous fluctuations in exhaust superheat during system operation, ensuring that the determined first superheat condition is the true and stable operating state of the HVAC system, and avoiding the misjudgment of brief low superheat fluctuations as continuous low superheat operation.

[0035] For the second superheat condition, including two situations: exhaust superheat ≤ preset critical superheat value but the state duration does not reach the preset duration, and exhaust superheat > preset critical superheat value, it achieves full coverage of all operating states except the first superheat condition, so that the HVAC system's operating condition type determination has no blind spots, ensuring that the corresponding operating condition type can be matched under any operating state, and ensuring the continuity of subsequent oil return control.

[0036] In one possible implementation, in step 104, when the operating condition type is a high superheat condition, oil return control parameters are determined based on the operating condition type, and an oil return operation is performed based on the oil return control parameters. This includes: acquiring the hardware parameters of the HVAC system, wherein the hardware parameters are hardware parameters that affect the oil return effect under the high superheat condition; determining the minimum effective refrigerant return flow rate to meet the first basic oil return requirement of the system based on the hardware parameters, with the goal of effectively returning the accumulated refrigerant oil in the pipeline to the compressor; calculating the first target oil return frequency and the first target oil return time based on the first minimum effective refrigerant return flow rate; the first target oil return time is used to define the preset oil return completion condition; determining the current oil-accumulating component based on the current operating mode of the HVAC system; adjusting the expansion valve corresponding to the current oil-accumulating component to a preset increased opening range, and controlling the compressor to operate at the first target oil return frequency.

[0037] This implementation refines the differentiated oil return control operation and oil return mode exit mechanism in step 104. It designs an adaptable oil return control process for both high and low superheat conditions, and formulates oil return completion judgment and exit rules that are precisely matched with the oil return control parameters. This solves the problems that traditional single oil return strategies cannot adapt to different superheat conditions of HVAC systems and are prone to insufficient oil return, excessive oil return, or compressor oil discharge shortage. It achieves precise and differentiated oil return control based on the actual operating conditions of the system, taking into account both oil return effect and compressor operation safety, and forming a complete oil return control closed loop.

[0038] For high superheat conditions, the primary requirement for system oil return is to effectively return accumulated refrigerant oil in the pipeline to the compressor. First, the hardware parameters of the equipment affecting the oil return effect under this condition are obtained. Based on these parameters, the minimum effective refrigerant return flow rate to meet the oil return requirement is determined. Then, based on this flow rate, the first target oil return frequency and the first target oil return time are calculated. Simultaneously, the oil-accumulating components are identified in conjunction with the current operating mode of the HVAC system. By adjusting the corresponding expansion valve to a preset increased opening range and controlling the compressor to operate at the first target oil return frequency, the system refrigerant flow rate reaches the minimum effective refrigerant return flow rate. The entire process aligns with the operating characteristics of high superheat conditions, achieving rapid flushing and return of accumulated oil in the pipeline by increasing the refrigerant flow rate, ensuring oil return efficiency. Furthermore, by using equipment hardware parameters as the core basis, the refrigerant flow rate and oil return control parameters are adapted to the system's own hardware characteristics.

[0039] In one possible implementation, in step 104, when the operating condition type is a low superheat condition, oil return control parameters are determined based on the operating condition type, and an oil return operation is performed based on the oil return control parameters. This includes: acquiring the fluid hardware parameters of the HVAC system, wherein the fluid hardware parameters are hardware parameters that affect the oil return effect under the low superheat condition; taking the effective return of accumulated refrigerant oil in the pipeline to the compressor while suppressing the compressor's oil discharge as the second basic requirement for oil return of the system; determining the second minimum effective refrigerant return flow rate to meet the second basic requirement for oil return of the system based on the fluid hardware parameters; calculating the second target oil return frequency and the second target oil return time based on the second minimum effective refrigerant return flow rate; the second target oil return time is used to define the preset oil return completion condition; the second target oil return time is greater than the first target oil return time; controlling the compressor to operate at the second target oil return frequency, wherein the second target oil return frequency is less than the first target oil return frequency.

[0040] For low superheat conditions, considering the high oil discharge rate of the compressor, a second basic requirement for system oil return was set. This means achieving effective return of accumulated refrigerant oil in the pipeline while suppressing compressor oil discharge. First, the fluid hardware parameters affecting the oil return effect under this condition were obtained, and the minimum effective return flow rate of the second refrigerant to meet this requirement was determined. Then, the second target oil return frequency and the second target oil return time were calculated. The second target oil return frequency was limited to be less than the first target oil return frequency, and the second target oil return time was limited to be greater than the first target oil return time. The compressor was controlled to run continuously at this low frequency without adjusting the opening of the expansion valve. This design avoids the problem of increased compressor oil discharge caused by frequency increase operation. The refrigerant oil return is achieved through low-frequency long-term operation, and the oil return is completed while ensuring the safe oil level of the compressor.

[0041] In one possible implementation, step 104, exiting the oil return mode after satisfying a preset oil return completion condition, includes: real-time statistics of the first cumulative operating time of the compressor running at the first target oil return frequency, and determining that the preset oil return completion condition is satisfied based on the first cumulative operating time reaching the first target oil return time; or, real-time statistics of the second cumulative operating time of the compressor running at the second target oil return frequency, and determining that the preset oil return completion condition is satisfied based on the second cumulative operating time reaching the second target oil return time; based on satisfying the preset oil return completion condition, controlling the HVAC system components to return to the operating state before entering the oil return mode, thereby exiting the oil return mode.

[0042] This implementation also includes a mechanism for determining oil return completion and exiting the oil return mode, precisely matching the oil return control parameters for the two operating conditions. For high and low superheat conditions, the cumulative running time of the compressor at the corresponding target oil return frequency is counted in real time. When the cumulative running time reaches the target oil return time, the preset oil return completion condition is determined to be met. This determination method uses the oil return control parameters as the core basis, providing a clear and quantifiable standard for the oil return completion condition, thus avoiding insufficient or excessive oil return. After the determination is met, all components of the HVAC system are restored to their operating state before entering the oil return mode, completing the exit from the oil return mode. This ensures that the system can quickly resume normal operation after the oil return operation is completed, without affecting the routine operation of the HVAC system.

[0043] The design of the aforementioned differentiated oil return control and closed-loop exit mechanism ensures precise adaptation of oil return operations under high and low superheat conditions, from basic requirements, parameter basis, control parameters to execution methods. This effectively solves the adaptability problem of traditional single oil return strategies under different superheat conditions, ensuring effective return of oil accumulated in the pipeline while avoiding adverse effects on the compressor caused by improper oil return operations.

[0044] In summary, after the system enters the oil return mode when the oil return trigger condition is met, the system exhaust superheat at startup is first detected. Then, the current operating condition type is determined by comparing the exhaust superheat with a preset threshold and considering the duration of the state. Finally, the corresponding oil return control parameters are matched based on the operating condition type, and the oil return operation is executed until the oil return completion condition is met, at which point the system exits. Through this logic, this method can accurately identify low superheat operating conditions, avoiding the drawbacks of directly increasing the frequency for oil return in low superheat scenarios in existing technologies. Differentiated oil return control parameters ensure the oil return effect while guaranteeing oil return efficiency under high superheat operating conditions, ultimately achieving stable maintenance of the compressor's safe oil level under all operating conditions.

[0045] Figure 2 This diagram illustrates the structure and refrigerant circulation principle of the HVAC system to which this application applies in cooling and defrosting modes. The HVAC system provides complete physical hardware support for the implementation of the adaptive oil return control method. The system mainly includes an indoor unit and an outdoor unit connected by refrigerant piping. Core components include a compressor, a four-way valve, an outdoor heat exchanger, an indoor heat exchanger, an indoor expansion valve, an outdoor expansion valve, a liquid receiver, and a gas-liquid separator. The compressor is the core actuator for the oil return operation, and its operating frequency is dynamically adjusted according to the target oil return frequency determined by the method of this application and matched to the current operating conditions. The four-way valve is used to switch between cooling and heating cycles; the diagram represents the connection state in cooling mode.

[0046] To achieve adaptive oil return control, the system is equipped with a detection element: an exhaust temperature sensor T1 is installed on the compressor exhaust pipe to collect the exhaust temperature in real time. Combined with the pressure signal collected by the high-pressure sensor on the high-pressure side of the system, the high-pressure saturation temperature can be calculated based on the refrigerant properties. The exhaust superheat (DSH) is calculated from the difference between the exhaust temperature and the high-pressure saturation temperature, and serves as the basis for determining whether the current operating state is low or high superheat when the system enters oil return mode.

[0047] The refrigerant circulation path in cooling mode is described below. The compressor discharges high-temperature, high-pressure gaseous refrigerant, which flows through a four-way valve to the outdoor heat exchanger, where it acts as a condenser, releasing heat through condensation. The condensed high-pressure liquid refrigerant then passes through a liquid pipe and the indoor expansion valve for throttling and pressure reduction before entering the indoor heat exchanger to absorb heat and evaporate. The evaporated low-temperature, low-pressure gaseous refrigerant returns to the compressor through a gas pipe, a four-way valve, and a gas-liquid separator. In this mode, lubricating oil tends to accumulate in the indoor heat exchanger on the low-temperature, low-pressure side and in the connected gas pipes. This area is the key area for oil accumulation that needs to be flushed during the oil return operation.

[0048] Once the system meets the oil return trigger conditions and enters the oil return mode, it will perform differentiated control based on the real-time exhaust superheat. When a high superheat condition is detected, the system controls the indoor expansion valve opening to increase to a preset range, thereby increasing the evaporation pressure. Simultaneously, the compressor is controlled to operate at a higher first target oil return frequency Hzoil2, using a large flow of refrigerant to quickly flush away accumulated oil in the pipes. When a low superheat condition is detected, to reduce the risk of compressor oil discharge, the system controls the compressor to operate at a lower second target oil return frequency Hzoil1 for a longer second target oil return time Toil1, while maintaining the indoor expansion valve opening or making only minor adjustments to avoid refrigerant liquid return due to excessively low superheat. The core of this adaptive strategy is to ensure a safe and stable oil return process by using low-frequency operation, extended duration, and careful adjustment of throttling components under low superheat conditions.

[0049] After the oil return operation reaches the preset time requirement, the system controls all relevant components to return to their operating state before the oil return initiation and exits the oil return mode. The system also includes an oil return auxiliary circuit consisting of an oil separator, an oil return capillary tube, and a check valve. Ambient temperature sensor T3 and return gas temperature sensor T4 provide operating parameters for the system, while defrosting temperature sensor T2 coordinates the oil return action with system defrosting and other protection logic.

[0050] Figure 3 The following are examples of embodiments provided in this application. Figure 2 The consistent operating principle of a heating, ventilation, and air conditioning system in heating mode. Figure 2 In comparison, the main difference lies in the fact that the four-way valve completes the reversal, thereby changing the refrigerant flow direction and the working function of each heat exchanger.

[0051] In heating mode, the high-temperature, high-pressure gaseous refrigerant discharged from the compressor flows directly to the indoor heat exchanger through a four-way valve. At this time, the indoor heat exchanger acts as a condenser, releasing heat into the indoor space. The condensed high-pressure liquid refrigerant, after passing through the liquid pipe and the outdoor expansion valve, enters the outdoor heat exchanger to absorb heat from the outdoor environment and complete evaporation. The evaporated low-temperature, low-pressure gaseous refrigerant returns to the compressor through the four-way valve. In heating mode, lubricating oil mainly accumulates on the low-temperature side of the outdoor heat exchanger and in the connected return gas line.

[0052] When performing oil return operation in heating mode, the four-way valve is typically switched to briefly switch the system to a refrigeration cycle, allowing the high-temperature, high-pressure exhaust gas to directly flush the outdoor heat exchanger, which is the main oil accumulation area. The adaptive control strategy of this application also applies in heating mode. Under high superheat conditions, after the four-way valve switches, the system increases the opening of the outdoor expansion valve and controls the compressor to run at high speed at the first target oil return frequency, achieving rapid and efficient oil return. Low superheat conditions are more common in heating mode, especially during low-temperature, low-load operation. In this case, after the four-way valve switches, the system controls the compressor to run continuously at a low frequency at the second target oil return frequency, maintaining or slightly adjusting the opening of the outdoor expansion valve, significantly reducing the risk of oil discharge while ensuring effective oil return.

[0053] After the oil return process is completed, the system controls all components, including the four-way valve, expansion valve, and compressor, to return to normal heating operation. Through this control method, the system can maintain a safe oil level in the compressor under any operating mode, while minimizing the impact of the oil return operation on the main operating function of the air conditioner.

[0054] Based on the aforementioned hardware foundation of the HVAC system, the refrigerant circulation and oil accumulation characteristics of each operating mode, the following section further details the specific logic flow of the adaptive oil return control method of this application, clarifying the complete control process from oil return triggering to exit. Figure 4 This is a schematic diagram of the logic flow of the adaptive oil return control method of this application, showing the logic from oil return mode triggering, operating condition determination, differentiated oil return execution to exiting oil return. The adaptive adjustment of the oil return strategy is achieved by dynamically determining the exhaust superheat.

[0055] First, when the oil return conditions are met, the system enters the oil return mode. These conditions typically involve the system's cumulative running time reaching a preset cycle, or the oil return discharge volume dropping to a preset minimum value. This ensures that the oil return operation is only initiated when necessary, avoiding unnecessary operational interference. After entering the oil return mode, the system first detects the discharge superheat (DSH) at the moment of entry into oil return mode. This parameter is calculated by subtracting the system's high-pressure saturation temperature from the compressor discharge temperature and is the core basis for determining the system's current operating condition.

[0056] Next, the system proceeds to the operating condition determination stage: it determines whether the exhaust superheat DSH is less than or equal to the preset low exhaust superheat value DSHL, and whether the duration of this state reaches the preset low exhaust time Dtime. This dual determination logic is designed to eliminate the interference of instantaneous fluctuations in exhaust superheat and ensure that only stable low superheat states are determined as low-load operating conditions.

[0057] If the determination is yes, the system enters the low superheat oil return process: the compressor is controlled to run continuously at a low superheat oil return frequency Hzoil1, which is less than the high superheat oil return frequency Hzoil2. The purpose is to reduce the compressor's oil discharge rate and avoid abnormal oil level drops under low load. At the same time, it continues to run until the low superheat operating time Toil1 is met, which is longer than the high superheat operating time Toil2, to compensate for the lower refrigerant oil carrying efficiency under low frequency operation. If Toil1 is not reached, operation continues; once the target is met, the oil return process is triggered to exit.

[0058] If the determination is negative, i.e., the exhaust superheat DSH is greater than DSHL, or the duration of the low superheat state is less than Dtime, the system will enter the high superheat oil return process: control the compressor to run continuously at the high superheat oil return frequency Hzoil2, increase the refrigerant flow through the high frequency, and quickly flush the oil accumulated in the pipeline; at the same time, continue to run until the high superheat running time Toil2 is met, and trigger the exit of oil return after the standard is met, otherwise continue to maintain the current running frequency.

[0059] Throughout the process, the oil return frequencies Hzoil1 and Hzoil2, and the oil return times Toil1 and Toil2 are all adaptive values ​​calculated based on hardware parameters such as system pipe length, pipe diameter, and compressor oil discharge rate. These values ​​are coordinated with the expansion valve's linkage control; for example, the valve opens to its maximum opening during high superheat oil return and maintains its current opening during low superheat oil return. This ensures effective oil return under different operating conditions while suppressing the risk of compressor oil discharge under low superheat conditions, ultimately achieving a stable and safe oil level maintenance for the compressor and improving the reliability of the system throughout its entire lifecycle.

[0060] In summary, this application provides a method for controlling oil return in a heating and ventilation system (HVAC) system. The method involves determining when the HVAC system meets a preset oil return trigger condition and entering an oil return mode; determining the exhaust superheat at the start of the oil return mode; determining the current operating condition type of the HVAC system based on the exhaust superheat; determining oil return control parameters based on the operating condition type; and executing an oil return operation based on the oil return control parameters until a preset oil return completion condition is met, at which point the method exits the oil return mode. This addresses the problem of traditional HVAC system oil return control using a single strategy that fails to adjust the oil return method according to the exhaust superheat characteristics, leading to incomplete oil return, compressor oil discharge, or oil shortage. The method achieves precise oil return control based on operating conditions. After the oil return mode is started when the preset trigger condition is met, the method uses the comparison between the exhaust superheat and a preset critical value, combined with the duration of the state, to distinguish different operating conditions of the HVAC system. It then matches appropriate oil return control parameters to different operating conditions, thereby formulating and executing targeted oil return operations, ensuring that the oil return strategy is adapted to the actual superheat conditions of the system. While ensuring effective flushing of oil accumulation in the pipeline, it is crucial to avoid improper oil return operations that could affect the compressor's operating status, ultimately ensuring the reliable operation of the HVAC system compressor and improving the adaptability and effectiveness of oil return control.

[0061] Based on the same technical concept, embodiments of this application also provide a heating and ventilation system oil return control device, such as... Figure 5 As shown, the device includes: The oil return mode determination module 501 is used to determine whether the HVAC system meets the preset oil return trigger conditions and enters the oil return mode. The exhaust superheat module 502 is used to determine the exhaust superheat at the start of the oil return mode. Operating condition determination module 503 is used to determine the current operating condition type of the HVAC system based on the exhaust superheat. The oil return control module 504 is used to determine the oil return control parameters based on the operating condition type, and to perform the oil return operation based on the oil return control parameters until the preset oil return completion condition is met and then exit the oil return mode.

[0062] This application also provides an electronic device corresponding to the method provided in the foregoing embodiments. Please refer to... Figure 6 The diagram illustrates an electronic device provided by some embodiments of this application. The electronic device 20 may include: a processor 200, a memory 201, a bus 202, and a communication interface 203, wherein the processor 200, the communication interface 203, and the memory 201 are connected via the bus 202; the memory 201 stores a computer program that can run on the processor 200, and when the processor 200 runs the computer program, it executes the method provided by any of the foregoing embodiments of this application.

[0063] The memory 201 may include high-speed random access memory (RAM) or non-volatile memory, such as at least one disk storage device. Communication between this system network element and at least one other network element is achieved through at least one physical port (which can be wired or wireless), such as the Internet, wide area network, local area network, or metropolitan area network.

[0064] Bus 202 can be an ISA bus, PCI bus, or EISA bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. The memory 201 is used to store programs. After receiving an execution instruction, the processor 200 executes the program. The method disclosed in any of the foregoing embodiments of this application can be applied to the processor 200, or implemented by the processor 200.

[0065] The processor 200 may be an integrated circuit chip with signal processing capabilities. In implementation, each step of the above method can be completed by the integrated logic circuitry in the hardware of the processor 200 or by instructions in software form. The processor 200 may be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it may also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), an off-the-shelf programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor may be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this application can be directly embodied in the execution of a hardware decoding processor, or executed by a combination of hardware and software modules in the decoding processor. The software modules may reside in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. The storage medium is located in memory 201. The processor 200 reads the information in memory 201 and, in conjunction with its hardware, completes the steps of the above method.

[0066] The electronic devices and methods provided in the embodiments of this application are based on the same inventive concept and have the same beneficial effects as the methods they employ, operate, or implement.

[0067] This application also provides a computer-readable storage medium corresponding to the method provided in the foregoing embodiments. Please refer to... Figure 7The computer-readable storage medium shown is an optical disc 30, on which a computer program (i.e., a program product) is stored, which, when run by a processor, executes the methods provided in any of the foregoing embodiments.

[0068] It should be noted that examples of the computer-readable storage medium may also include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other optical and magnetic storage media, which will not be elaborated here.

[0069] The computer-readable storage medium provided in the above embodiments of this application and the method provided in the embodiments of this application are based on the same inventive concept and have the same beneficial effects as the methods adopted, run or implemented by the applications stored therein.

[0070] It should be noted that the above embodiments are illustrative of this application and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. This application can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0071] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0072] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made under the concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for controlling oil return in a heating, ventilation, and air conditioning system, characterized in that, The method includes: Once the HVAC system meets the preset oil return trigger conditions, it enters the oil return mode. Determine the exhaust superheat at the moment the return oil mode is activated; The current operating condition type of the HVAC system is determined based on the exhaust superheat. The return oil control parameters are determined based on the operating condition type, and the return oil operation is performed based on the return oil control parameters until the preset return oil completion condition is met and then the return oil mode is exited.

2. The method as described in claim 1, characterized in that, The current operating condition type of the HVAC system is determined based on the exhaust superheat, including: Based on the fact that the exhaust superheat is less than or equal to a preset critical superheat value, and the duration of the state where the exhaust superheat is less than or equal to the preset critical superheat value reaches a preset duration, the operating condition type of the HVAC system is determined to be the first superheat condition. The operating condition type of the HVAC system is determined to be the second superheat condition based on the exhaust superheat being less than or equal to the preset critical superheat value and the duration of the state not reaching the preset duration, or based on the exhaust superheat being greater than the preset critical superheat value. The exhaust superheat corresponding to the first superheat condition is less than or equal to the preset critical superheat value, the exhaust superheat corresponding to the second superheat condition is greater than the preset critical superheat value, and the exhaust superheat under the second superheat condition is greater than the exhaust superheat under the first superheat condition.

3. The method as described in claim 2, characterized in that, When the operating condition is a high superheat condition, the oil return control parameters are determined based on the operating condition type, and the oil return operation is performed based on the oil return control parameters, including: Obtain the equipment hardware parameters of the HVAC system, wherein the equipment hardware parameters are the hardware parameters that affect the oil return effect under high superheat conditions; The first basic requirement for system oil return is to ensure that the accumulated refrigerant oil in the pipeline is effectively returned to the compressor. Based on the hardware parameters of the equipment, the minimum effective refrigerant return flow rate that meets the first basic requirement for system oil return is determined. The first target oil return frequency and the first target oil return time are calculated based on the minimum effective return flow rate of the first refrigerant; the first target oil return time is used to define the preset oil return completion conditions. Determine the currently oil-accumulating component based on the current operating mode of the HVAC system; Adjust the expansion valve corresponding to the currently oil-accumulating component to a preset increased opening range, and control the compressor to operate at the first target oil return frequency.

4. The method as described in claim 3, characterized in that, When the operating condition is a low superheat condition, the oil return control parameters are determined based on the operating condition type, and the oil return operation is performed based on the oil return control parameters, including: Obtain the fluid hardware parameters of the HVAC system, wherein the fluid hardware parameters are the hardware parameters that affect the oil return effect under low superheat conditions; The second basic requirement for oil return in the system is to effectively return the accumulated refrigerant oil in the pipeline to the compressor while suppressing the compressor's oil discharge. The minimum effective return flow rate of the second refrigerant that meets the second basic requirement for oil return in the system is determined based on the fluid hardware parameters. The second target oil return frequency and the second target oil return time are calculated based on the minimum effective return flow rate of the second refrigerant; the second target oil return time is used to define the preset oil return completion condition; the second target oil return time is greater than the first target oil return time. The compressor is controlled to operate at the second target oil return frequency, wherein the second target oil return frequency is less than the first target oil return frequency.

5. The method as described in claim 4, characterized in that, The oil return mode will exit once the preset oil return completion conditions are met, including: The compressor's first cumulative operating time at the first target oil return frequency is statistically analyzed in real time. Based on the first cumulative operating time reaching the first target oil return time, it is determined that the preset oil return completion condition has been met; or... The second cumulative running time of the compressor running at the second target oil return frequency is counted in real time. Based on the second cumulative running time reaching the second target oil return time, it is determined that the preset oil return completion condition is met. Based on meeting the preset oil return completion conditions, the HVAC system components are controlled to return to their operating state before entering the oil return mode, so as to exit the oil return mode.

6. The method as described in claim 1, characterized in that, Determine the exhaust superheat at the moment of oil return mode activation, including: Collect the compressor's exhaust temperature and the high-pressure side pressure of the HVAC system; The high-pressure saturation temperature is obtained based on the high-pressure side pressure conversion. The difference between the exhaust temperature and the high-pressure saturation temperature is calculated as the exhaust superheat.

7. The method as described in claim 1, characterized in that, The HVAC system is confirmed to meet preset return oil trigger conditions and enters return oil mode, including: Real-time monitoring of the cumulative operating time of the HVAC system, and real-time calculation of the HVAC system's oil return and air venting volume; If the cumulative operating time of the HVAC system reaches a preset periodic oil return interval, then the HVAC system is determined to meet the preset oil return trigger condition and enters the oil return mode; and / or, If the return oil and exhaust volume of the HVAC system reaches the preset minimum return oil and exhaust volume, then the HVAC system is determined to meet the preset return oil trigger condition and enters the return oil mode.

8. A return oil control device for a heating, ventilation, and air conditioning system, characterized in that, The device includes: The oil return mode determination module is used to determine whether the HVAC system meets the preset oil return trigger conditions and enters the oil return mode; The exhaust superheat module is used to determine the exhaust superheat at the start of the oil return mode. The operating condition determination module is used to determine the current operating condition type of the HVAC system based on the exhaust superheat. The oil return control module is used to determine the oil return control parameters based on the operating condition type, and to perform the oil return operation based on the oil return control parameters until the preset oil return completion condition is met and then exit the oil return mode.

9. An electronic device, comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor, when running the computer program, performs an action to implement the method as claimed in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, It stores computer-readable instructions that can be executed by a processor to implement the method as described in any one of claims 1-7.

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