air conditioner

Abstract

This application discloses an air conditioner, relating to the technical field of air conditioning. The air conditioner has a circulating preheating mode. The air conditioner includes an outdoor unit, an indoor unit, a refrigerant circulation pipeline, a refrigerant pump, a solenoid valve, a one-way valve, and an electric heating device. The outdoor unit contains a compressor, a four-way reversing valve, an outdoor heat exchanger, an electronic expansion valve, and a gas-liquid separator. The indoor unit contains an indoor heat exchanger. The refrigerant circulation pipeline connects the outdoor unit and the indoor unit, forming a refrigerant circulation loop. The refrigerant pump is connected in series between the outdoor heat exchanger and the electronic expansion valve; the solenoid valve is connected in parallel between the inlet and outlet of the refrigerant pump; the one-way valve is connected in parallel between the compressor's suction port and discharge port; and the electric heating device is wound around the outer wall of the gas-liquid separator. When the low-temperature start-up conditions are met, the air conditioner enters the circulating preheating mode to preheat the refrigerant before switching to heating mode. The air conditioner provided by this application can improve low-temperature start-up performance, protect the compressor, and shorten the heating waiting time.

Description

Technical Field

[0001] This application relates to the technical field of air conditioning, and more particularly to an air conditioner. Background Technology

[0002] In practical applications of air conditioning systems (including multi-split systems and unit systems), the preheating of the unit after a long period of static operation in a low-temperature environment is crucial to the stable and reliable operation of the unit during the startup phase.

[0003] In related technologies, the preheating method for the unit involves wrapping an electric heating strip around the compressor body. This method can only preheat the refrigerant stored inside the compressor. The refrigerant does not circulate and remains relatively static, relying primarily on heat conduction for localized heating. This static, localized heating method results in two main problems: firstly, extremely low refrigerant preheating efficiency, with the longest preheating time reaching 4 hours; secondly, because the refrigerant cannot circulate, it cannot uniformly preheat all the refrigerant in the system, leading to problems such as excessively low pressure after unit startup. Furthermore, excessive liquid refrigerant in the piping can cause liquid-laden compressor startup and liquid slugging failures, or the mixing of low-temperature refrigerant with compressor oil can lead to a drop in compressor oil level, among other reliability issues.

[0004] Fluorine pump technology is an energy-saving technology that drives the circulation of refrigerant through a pump. It is currently widely used in the refrigeration cycle system of computer room air conditioning. It mainly achieves heat transfer by driving the refrigerant circulation through a fluorine pump under low ambient temperature refrigeration conditions. Compared with the compressor-driven circulation method, it has better energy efficiency.

[0005] Currently, some technologies have attempted to apply refrigerant pump technology to low-temperature start-up scenarios in heat pump systems. This involves introducing heated refrigerant into the compressor suction port via a refrigerant pump to achieve preheating for low-temperature startup. However, this approach still has significant technical limitations: First, the refrigerant cannot form a complete circulation flow. This non-circulating refrigerant delivery method results in low refrigerant heating efficiency, easily leading to the refrigerant being introduced into the compressor suction port before being fully preheated and unable to be reheated after entering the compressor. Second, the refrigerant is often heated by winding pipes, which, due to the limited contact area between the refrigerant and the heating components, directly results in slow heating speed and poor preheating effect. Third, the refrigerant cannot achieve system-level circulation. A large amount of refrigerant continuously accumulates on the compressor suction side, which cannot hold all the system's refrigerant. As the refrigerant pump continuously introduces system refrigerant into the compressor suction port, the suction side pressure continuously increases, easily leading to liquefaction of the gas-liquid mixture of refrigerant. This significantly increases the risk of liquid return during compressor startup and fails to fundamentally solve the technical problem of liquid carryover during low-temperature startup. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this application provides an air conditioner that solves the problems of difficulty in starting at low temperatures, easy damage to the compressor due to liquid slugging, slow heating response, and long waiting times for users. By driving the refrigerant to circulate throughout the entire circuit and uniformly preheating the refrigerant before starting the compressor, the refrigerant is fully vaporized before starting the compressor, thus fundamentally avoiding liquid slugging, significantly improving low-temperature start-up performance, and greatly shortening heating waiting time.

[0007] This application provides an air conditioner having a circulating preheating mode, the air conditioner comprising: The outdoor unit is used for heat exchange with the outdoor environment. The outdoor unit contains a compressor, a four-way reversing valve, an outdoor heat exchanger, an electronic expansion valve, and a gas-liquid separator. The indoor unit is used to exchange heat with indoor air in order to regulate the indoor air and achieve cooling or heating. The indoor unit is equipped with an indoor heat exchanger. The refrigerant circulation pipeline connects the outdoor unit and the indoor unit, connecting the compressor, four-way reversing valve, indoor heat exchanger, electronic expansion valve, outdoor heat exchanger and gas-liquid separator in sequence to form a closed refrigerant circulation loop; the compressor is used to drive the refrigerant to circulate in the refrigerant circulation loop in heating mode. A refrigerant pump, connected in series in the refrigerant circulation pipeline between the outdoor heat exchanger and the electronic expansion valve, is used to drive the refrigerant to circulate in the refrigerant circulation loop in the circulation preheating mode. A solenoid valve is connected in parallel between the inlet and outlet of the fluorine pump; A one-way valve is connected in parallel between the suction port and the discharge port of the compressor. The one-way valve is directed from the suction port of the compressor to the discharge port. It is used to allow the refrigerant to flow through and bypass the compressor in the circulating preheating mode. An electric heating device is wound around the outer wall of the gas-liquid separator to preheat the refrigerant circulating through the gas-liquid separator; In the circulating preheating mode, the solenoid valve is closed, the one-way valve is open, the electric heating device is turned on, and the refrigerant pump drives the refrigerant to circulate in the refrigerant circulation loop and preheat the circulating refrigerant.

[0008] This technical solution addresses the core issues of refrigerant liquefaction and compressor damage during air conditioner startup in low-temperature environments. It constructs an independent refrigerant pump preheating circulation system through the synergistic interaction of various features: the outdoor and indoor units form the basic heat exchange carriers, and the refrigerant circulation pipeline provides the circulation channel; the refrigerant pump provides an independent power source for the preheating stage, replacing the compressor to drive the refrigerant circulation; the solenoid valve enables bypass switching of the refrigerant pump in different modes; the check valve bypasses the compressor during the preheating stage, forming a complete preheating circulation loop; and the electric heating device directly and uniformly preheats the refrigerant circulating through the gas-liquid separator. These features work together to achieve full-range refrigerant circulation preheating even when the compressor is completely stopped, creating conditions for safe compressor startup.

[0009] In some embodiments, the air conditioner also includes detection components, including an outdoor ambient temperature sensor, a compressor exhaust temperature sensor, and a low-pressure sensor. An outdoor ambient temperature sensor is located on the casing of the outdoor unit and is used to detect the outdoor ambient temperature where the air conditioner is located. The compressor discharge temperature sensor is located at the compressor discharge port and is used to detect the compressor discharge temperature. The low-pressure sensor is located on the inlet pipe of the gas-liquid separator and is used to detect the low-pressure side pressure of the refrigerant circulation loop in the air conditioner.

[0010] This technical solution provides comprehensive and accurate data support for low-temperature start-up determination, preheating process monitoring, and preheating completion determination through multi-sensor collaborative detection, ensuring the accuracy and reliability of the control logic.

[0011] In some embodiments, the air conditioner also includes a controller configured to: upon receiving a heating start command, determine whether the air conditioner meets the low-temperature start conditions; if so, control the air conditioner to enter the circulating preheating mode; if not, control the air conditioner to enter the heating mode.

[0012] This technical solution uses a controller to coordinate the operation of all components, achieving automated control of the low-temperature start-up and preheating process without manual intervention, thus improving the user experience.

[0013] In some embodiments, the controller is further configured to: Obtain the outdoor ambient temperature Ta and the compressor exhaust temperature Td, and preset the low-temperature start-up threshold conditions for the air conditioner. The low-temperature start-up threshold conditions include: the outdoor ambient temperature Ta reaches the preset low-temperature start-up upper limit temperature threshold Tao, and the compressor exhaust temperature Td reaches the preset low-temperature start-up exhaust temperature threshold Tdo. When the detected outdoor ambient temperature Ta and compressor exhaust temperature Td simultaneously meet the low-temperature start-up threshold condition, the air conditioner is determined to meet the low-temperature start-up condition. If either the detected outdoor ambient temperature Ta or the compressor exhaust temperature Td does not meet the low-temperature start-up threshold condition, the air conditioner is determined not to meet the low-temperature start-up condition.

[0014] This technical solution determines the low-temperature start-up conditions of the air conditioner by combining the outdoor ambient temperature and the compressor exhaust temperature, ensuring that the circulating preheating mode is activated only in low-temperature environments where preheating is truly required, thus avoiding unnecessary energy consumption and improving system operating efficiency.

[0015] In some embodiments, the controller is further configured to: When the air conditioner enters the circulating preheating mode, perform the following operations: close the solenoid valve, de-energize the four-way reversing valve, fully open the electronic expansion valve, start the refrigerant pump, and turn on the electric heating device.

[0016] This technical solution uses synchronous linkage control of various components to quickly build a complete preheating circulation loop, ensuring that the refrigerant can circulate stably and be fully preheated when the compressor is stopped, thus making full preparations for compressor startup.

[0017] In some embodiments, the controller is further configured to: When the air conditioner enters the circulating preheating mode, the refrigerant pump is controlled to start running at a preset initial operating frequency; During operation in the circulating preheating mode, the operating frequency of the fluorine pump is calculated and adjusted every preset adjustment cycle; The calculation and adjustment method for the operating frequency of the fluorine pump is as follows: based on the system low-pressure side pressure Ps(n) detected this time and the system low-pressure side pressure Ps(n-1) detected last time, calculate the pressure deviation value ΔPs(n) for this time and the pressure deviation value ΔPs(n-1) for the last time respectively. Based on the preset proportional coefficient Kp, the preset integral coefficient Ki, the current pressure deviation value △Ps(n) and the previous pressure deviation value △Ps(n-1), the frequency adjustment amount △Hzo of the current fluorine pump operation is calculated. Based on the previous operating frequency of the fluorine pump Hzo(n-1) and the current frequency adjustment ΔHzo, the current operating frequency of the fluorine pump Hzo(n) is calculated. Control the fluorine pump to operate at the calculated operating frequency Hzo(n), and control the operating frequency of the fluorine pump to be within the preset fluorine pump frequency range.

[0018] This technical solution uses a proportional-integral control algorithm to dynamically adjust the operating frequency of the refrigerant pump. It can adjust the refrigerant circulation speed in real time according to changes in system pressure, ensuring efficient and stable preheating process, while avoiding the impact of excessively high or low refrigerant pump operating frequency on system performance and service life.

[0019] In some embodiments, the controller is further configured to: After the air conditioner enters the circulating preheating mode, the system low-pressure side pressure Ps and compressor exhaust temperature Td are obtained in real time, and the threshold conditions for determining the completion of the air conditioner's circulating preheating are preset. The threshold conditions for determining the completion of cycle preheating include: the system low-pressure side pressure Ps reaches the preset low-pressure threshold Pso, and the compressor discharge temperature Td reaches the preset discharge temperature threshold Tdo. When the detected system low-pressure side pressure Ps and compressor exhaust temperature Td simultaneously meet the threshold conditions for completing the cycle preheating, the preheating is determined to be complete, and the air conditioner is controlled to exit the cycle preheating mode.

[0020] This technical solution uses the combined parameters of the system's low-pressure side pressure and the compressor's exhaust temperature to determine the preheating completion status. This accurately determines whether the refrigerant has fully vaporized, ensuring that the compressor will not suck in liquid refrigerant when it starts up. This fundamentally avoids liquid slugging, effectively protects the compressor's safety, and extends its service life.

[0021] In some embodiments, the controller is further configured to: When the air conditioner exits the circulating preheating mode, the preheating end transition operation is performed first: the solenoid valve is opened, the four-way reversing valve is de-energized, the electronic expansion valve is closed, the refrigerant pump stops running, and the electric heating device is turned off.

[0022] This technical solution smoothly switches the refrigerant circulation loop by setting up a dedicated preheating end transition operation, avoiding the impact of sudden system pressure changes on various components, and improving the stability and reliability of system operation.

[0023] In some embodiments, the controller is further configured to: After the preheating transition is completed, the compressor is started, the four-way reversing valve is powered on to switch to the heating direction, and the electronic expansion valve is switched to the heating dynamic adjustment mode, so the air conditioner enters the heating mode.

[0024] This technical solution achieves a seamless and smooth transition from the circulating preheating mode to the heating mode by orderly switching the working status of each component, ensuring a continuous and stable heating process and significantly reducing the user's waiting time for heating.

[0025] In some embodiments, the controller is further configured to: After the air conditioner enters the circulating preheating mode, the running time of the circulating preheating mode is accumulated in real time. If the cumulative running time of the circulating preheating mode reaches the preset maximum circulating preheating time threshold, but the circulating preheating completion judgment threshold is still not met, the air conditioner will exit the circulating preheating mode and trigger a preheating abnormality fault prompt. This technical solution prevents the system from being stuck in the cycle preheating mode for an extended period by setting a maximum cycle preheating time protection mechanism. At the same time, it promptly informs users of abnormal system status through preheating abnormality fault prompts, facilitating timely maintenance and repair.

[0026] The aforementioned air conditioner utilizes a refrigerant pump to drive the refrigerant to circulate throughout the system before the compressor starts. An electric heating device wrapped around the outer wall of the gas-liquid separator evenly preheats the circulating refrigerant, ensuring its complete vaporization before starting the compressor. This effectively solves the industry-wide problems of difficult air conditioner startup and compressor damage due to liquid slugging in low-temperature environments. Through a series of technical means, including dual-parameter joint judgment, synchronous linkage control, smooth transition switching, abnormal protection, and variable frequency regulation, a highly efficient, stable, and safe low-temperature startup preheating process is achieved. This significantly improves the air conditioner's low-temperature startup performance, greatly shortens heating waiting time, enhances user experience, and has significant engineering application value. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the overall logic of the low-temperature start-up preheating control for an air conditioner according to some embodiments. Figure 2 This is a flowchart of the control logic for determining low-temperature start-up of an air conditioner according to some embodiments; Figure 3 This is a flowchart of the control logic for the air conditioner's circulating preheating mode according to some embodiments; Figure 4 This is a flowchart of the control logic for determining the completion of air conditioner cycle preheating according to some embodiments; Figure 5 This is a flowchart of the preheating end transition control logic for an air conditioner according to some embodiments; Figure 6 This is a flowchart of the air conditioner heating mode switching control logic according to some embodiments; Figure 7 Here is a flowchart of the abnormal protection and manual control logic for the air conditioner's circulating preheating according to some embodiments; Figure 8 This is a flowchart of the inverter regulation control logic for an air conditioner's refrigerant pump, according to some embodiments. Figure 9 This is a schematic diagram of an air conditioner structure according to some embodiments; Figure 10 This is a schematic diagram of the refrigerant circulation path in the air conditioner's circulating preheating mode according to some embodiments; Figure 11 This is a schematic diagram of the refrigerant circulation path in the heating mode of an air conditioner according to some embodiments.

[0028] In the picture: 1. Outdoor unit; 11. Compressor; 12. Four-way reversing valve; 13. Outdoor heat exchanger; 14. Electronic expansion valve; 15. Gas-liquid separator; 2. Indoor unit; 21. Indoor heat exchanger; 3. Refrigerant circulation piping; 41. Fluorine pump; 42. Solenoid valve; 43. Check valve; 44. Electric heating device; 451. Outdoor ambient temperature sensor; 452. Compressor exhaust temperature sensor; 453. Low-pressure sensor. Detailed Implementation

[0029] To make the objectives and implementation methods of this application clearer, the exemplary implementation methods of this application will be clearly and completely described below with reference to the accompanying drawings of the exemplary embodiments of this application. Obviously, the exemplary embodiments described are only some embodiments of this application, and not all embodiments.

[0030] It should be noted that the brief descriptions of terms in this application are only for the convenience of understanding the embodiments described below, and are not intended to limit the embodiments of this application. Unless otherwise stated, these terms should be understood in their ordinary and common meaning.

[0031] The terms "first," "second," "third," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar or related objects or entities, and do not necessarily imply a specific order or sequence, unless otherwise specified. It should be understood that such terms are interchangeable where appropriate.

[0032] The terms “comprising” and “having”, and any variations thereof, are intended to cover but not exclude inclusion, for example, a product or device that includes a range of components is not necessarily limited to all of the components that are clearly listed, but may include other components that are not clearly listed or that are inherent to such product or device.

[0033] The air conditioner provided in this application can have various implementation forms, such as wall-mounted air conditioners, cabinet air conditioners, central air conditioners, ducted air conditioners, multi-split air conditioners, unit air conditioners, etc. This application does not make specific limitations on these.

[0034] The air conditioner has a preheating mode and a heating mode. It includes an outdoor unit 1, an indoor unit 2, and a refrigerant circulation pipe 3. The indoor unit 2 is located indoors and contains an indoor heat exchanger 21 for heat exchange with indoor air to regulate the air and achieve cooling or heating. The outdoor unit 1 is located outdoors and exchanges heat with the outdoor environment. It contains a compressor 11, a four-way reversing valve 12, an outdoor heat exchanger 13, an electronic expansion valve 14, and a gas-liquid separator 15. The outdoor heat exchanger 13 exchanges heat with outdoor air, and the compressor 11 drives the refrigerant to circulate in the refrigerant circulation loop in heating mode, providing energy support for indoor heat exchange. The refrigerant circulation pipe 3 connects the outdoor unit 1 and the indoor unit 2, sequentially connecting the compressor 11, the four-way reversing valve 12, the indoor heat exchanger 21, the electronic expansion valve 14, the outdoor heat exchanger 13, and the gas-liquid separator 15 to form a closed refrigerant circulation loop.

[0035] In low-temperature environments, especially in the frigid winters of northern my country where outdoor temperatures frequently drop below 0°C, air conditioners face numerous industry-wide challenges when starting up for heating. When an air conditioner has been idle for an extended period, the refrigerant saturation pressure drops significantly at low temperatures, causing a large amount of refrigerant to liquefy and deposit at the bottom of the outdoor heat exchanger 13 and the gas-liquid separator 15. This results in extremely low refrigerant pressure at the compressor 11's suction port, preventing a large amount of liquid refrigerant from vaporizing. If the compressor 11 is started directly at this time, it is highly susceptible to drawing in liquid refrigerant, causing liquid slugging, which can lead to serious malfunctions such as damage to the compressor 11 valve plates, bearing wear, and a drop in the compressor 11 oil level, significantly shortening the compressor 11's lifespan. Simultaneously, the difficulty in refrigerant vaporization at low temperatures and the slow build-up of system pressure result in a slow heating response from the air conditioner, requiring users to wait a considerable amount of time to feel the warm air, severely impacting the user experience.

[0036] In related technologies, to solve the low-temperature start-up problem, an electric heating belt is usually installed on the compressor 11 to preheat it. However, this method can only heat a small amount of refrigerant stored inside the compressor 11 and cannot preheat the refrigerant in the entire system. The system pressure build-up is still slow, with the longest preheating time reaching 4 hours, and it cannot fundamentally prevent liquid slugging. Some technologies use an electric heating device 44 installed on the outdoor heat exchanger 13, but the outdoor heat exchanger 13 is large in size and has a wide heat exchange area. The electric heating device 44 has low heating efficiency, high energy consumption, and is prone to local overheating, posing a safety hazard. Other technologies attempt to use a refrigerant pump 41 to assist in preheating, but this has drawbacks such as the refrigerant not forming a complete cycle, low heating efficiency, and the risk of refrigerant accumulation on the suction side of the compressor 11, increasing the risk of liquid return.

[0037] In this application, an independent low-temperature start-up preheating component is used to circulate and preheat the refrigerant throughout the system before the compressor 11 starts. The low-temperature start-up preheating component includes a refrigerant pump 41, a solenoid valve 42, a check valve 43, and an electric heating device 44. See appendix. Figure 9 A refrigerant pump 41 is connected in series on the refrigerant circulation pipeline 3 between the outdoor heat exchanger 13 and the electronic expansion valve 14, and is used to provide independent power for refrigerant circulation in the circulation preheating mode; a solenoid valve 42 is connected in parallel between the inlet and outlet of the refrigerant pump 41, and is used to conduct refrigerant and bypass the refrigerant pump 41 in the heating mode; a one-way valve 43 is connected in parallel between the suction port and the discharge port of the compressor 11, and the conduction direction of the one-way valve 43 is from the suction port of the compressor 11 to the discharge port, and is used to conduct refrigerant and bypass the compressor 11 in the circulation preheating mode; an electric heating device 44 is wound around the outer wall of the gas-liquid separator 15, and is used to uniformly heat the refrigerant circulating through the gas-liquid separator 15.

[0038] Furthermore, the low-temperature start-up preheating assembly also includes detection components, including an outdoor ambient temperature sensor 451, a compressor discharge temperature sensor 452, and a low-pressure sensor 453. The outdoor ambient temperature sensor 451 is located on the casing of the outdoor unit 1 and is used to detect the outdoor ambient temperature where the air conditioner is located. The compressor discharge temperature sensor 452 is located at the discharge port of the compressor 11 and is used to detect the discharge temperature of the compressor 11. The low-pressure sensor 453 is located on the inlet pipe of the gas-liquid separator 15 and is used to detect the low-pressure side pressure of the refrigerant circulation loop of the air conditioner.

[0039] This application employs a low-temperature start-up preheating component to circulate refrigerant throughout the system via a refrigerant pump 41 before compressor 11 starts. An electric heating device 44, wrapped around the outer wall of the gas-liquid separator 15, uniformly preheats the circulating refrigerant, ensuring complete vaporization before compressor 11 starts, thus preventing liquid slugging at its source. Simultaneously, through multi-sensor collaborative detection, segmented dual-parameter joint judgment, synchronous linkage control, smooth transition switching, abnormal protection, and variable frequency adjustment, the traditional preheating time is reduced from a maximum of 4 hours to less than 1 hour. This achieves a highly efficient, stable, and safe low-temperature start-up preheating process, significantly improving the air conditioner's low-temperature start-up performance and drastically shortening heating waiting time. It also solves problems such as excessively low pressure after startup and reduced oil level in compressor 11 found in related technologies.

[0040] The air conditioner also includes a controller, which is electrically connected to the detection component, compressor 11, refrigerant pump 41, solenoid valve 42, electric heating device 44, four-way reversing valve 12, and electronic expansion valve 14, respectively, to coordinate the operation of each component and realize the automated control of the low-temperature start-up preheating process.

[0041] The controller is configured to: upon receiving a heating start command, determine whether the air conditioner meets the low-temperature start conditions; if so, control the air conditioner to enter the circulating preheating mode; if not, control the air conditioner to directly enter the heating mode.

[0042] See appendix Figure 1 This paper illustrates the overall logic flow of the low-temperature start-up preheating control of the air conditioner according to this application, specifically including the following steps: S1, the controller receives the user's heating start-up command; S2, the controller acquires the outdoor ambient temperature Ta and the compressor discharge temperature Td; S3, the controller determines whether the air conditioner meets the low-temperature start-up conditions; S4, if the judgment result of S3 is "yes", the controller controls the air conditioner to enter the circulating preheating mode; S5, the controller monitors the system low-pressure side pressure Ps and the compressor discharge temperature Td in real time, and determines whether the circulating preheating completion judgment threshold condition is met; S6, if the judgment result of S5 is "yes", the controller controls the air conditioner to perform the preheating end transition operation; S7, after completing the preheating end transition operation, the controller controls the air conditioner to enter the heating mode; S8, if the judgment result of S3 is "no", the controller controls the air conditioner to directly enter the heating mode.

[0043] In this embodiment, the outdoor ambient temperature sensor 451, the compressor exhaust temperature sensor 452, and the low-pressure sensor 453 of the detection component transmit the detected signals to the controller in real time, providing accurate and reliable data support for the controller's control decisions.

[0044] In this embodiment, the controller can be a microcontroller, MCU, or dedicated control chip, electrically connected to the drive module of each actuator, and used to output control signals to adjust the operating status of each component. The refrigerant pump 41 is a variable frequency refrigerant pump, which can adjust the operating frequency within a preset refrigerant pump frequency range according to system requirements; the solenoid valve 42 is a normally closed solenoid valve, which is open when energized and closed when de-energized; the one-way valve 43 is a check valve, which only allows refrigerant to flow from the suction port of the compressor 11 to the discharge port; the electric heating device 44 uses silicone heating tape, which is evenly wrapped around the outer wall of the gas-liquid separator 15, providing high heating efficiency and safety.

[0045] The controller is further configured to: acquire the outdoor ambient temperature Ta through the outdoor ambient temperature sensor 451, acquire the compressor exhaust temperature Td through the compressor exhaust temperature sensor 452, and pre-store the air conditioner's low-temperature start judgment threshold conditions; the low-temperature start judgment threshold conditions include: the outdoor ambient temperature Ta reaches the preset low-temperature start upper limit temperature threshold Tao, and the compressor exhaust temperature Td reaches the preset low-temperature start exhaust temperature threshold Tdo; when the detected outdoor ambient temperature Ta and compressor exhaust temperature Td simultaneously meet the low-temperature start judgment threshold conditions, the air conditioner is determined to meet the low-temperature start conditions; when either the detected outdoor ambient temperature Ta or the compressor exhaust temperature Td does not meet the low-temperature start judgment threshold conditions, the air conditioner is determined not to meet the low-temperature start conditions.

[0046] See appendix Figure 2 The specific execution steps corresponding to the above low-temperature start-up determination and control logic are as follows: A1. The controller obtains the outdoor ambient temperature Ta through the outdoor ambient temperature sensor 451; A2. The controller obtains the compressor exhaust temperature Td through the compressor exhaust temperature sensor 452; A3. The controller determines whether the outdoor ambient temperature Ta reaches the preset low-temperature start-up upper limit temperature threshold Tao; A4. If the determination result of A3 is "yes", the controller further determines whether the compressor exhaust temperature Td reaches the preset low-temperature start-up exhaust temperature threshold Tdo; A5. If the determination result of A4 is "yes", the controller determines that the air conditioner meets the low-temperature start-up conditions; A6. If the determination result of A3 or A4 is "no", the controller determines that the air conditioner does not meet the low-temperature start-up conditions.

[0047] In this embodiment, the preset low-temperature start-up upper limit temperature threshold Tao can be flexibly set according to the actual situation such as the model of the air conditioner and the climate conditions of the area where it is used, and is exemplarily set to 5°C; the preset low-temperature start-up exhaust temperature threshold Tdo is exemplarily set to 0°C. That is, when the outdoor ambient temperature is lower than 5°C and the compressor exhaust temperature is lower than 0°C, it is determined that the air conditioner needs to perform low-temperature start-up preheating.

[0048] By employing a dual-parameter determination method using both ambient temperature and exhaust temperature, it can accurately determine whether the air conditioner truly requires preheating. When the outdoor ambient temperature is high, even if the compressor exhaust temperature is low, the refrigerant can fully vaporize, eliminating the need for preheating. Conversely, when the compressor exhaust temperature is high, it indicates that the refrigerant within the system already has a certain temperature, further eliminating the need for preheating. This dual-parameter determination method avoids unnecessary preheating, reduces energy consumption, and improves system operating efficiency.

[0049] The controller is further configured to: when the air conditioner enters the circulating preheating mode, simultaneously execute the following linkage control operations: control the solenoid valve 42 to close, so that all the refrigerant in the refrigerant circulation loop flows through the refrigerant pump 41; control the four-way reversing valve 12 to de-energize (i.e., the cooling direction), locking the flow direction of the refrigerant circulation loop; control the electronic expansion valve 14 to remain fully open, reducing the flow resistance of the refrigerant pump 41 driving the refrigerant circulation; control the refrigerant pump 41 to start running, providing power for the refrigerant circulation; control the electric heating device 44 to start running, preheating the refrigerant circulating through the gas-liquid separator 15.

[0050] See appendix Figure 3 The specific execution steps corresponding to the above-mentioned circulating preheating mode control logic are as follows: B1. The controller determines that the air conditioner meets the low-temperature start-up conditions; B2. The controller controls the solenoid valve 42 to remain closed; B3. The controller controls the four-way reversing valve 12 to remain de-energized; B4. The controller controls the electronic expansion valve 14 to remain fully open; B5. The controller controls the refrigerant pump 41 to start operation; B6. The controller controls the electric heating device 44 to start operation; B7. The air conditioner enters the circulating preheating mode. It should be noted that B2-B6 are control operations executed synchronously by the controller. The step numbers are only for clear illustration of all operations and do not represent the order of operations.

[0051] In this embodiment, all control operations are executed synchronously, enabling the rapid construction of a complete preheating cycle loop. See Appendix. Figure 10 At this time, the refrigerant circulation path is: refrigerant pump outlet → electronic expansion valve → indoor heat exchanger → four-way reversing valve E port → four-way reversing valve S port → gas-liquid separator → check valve → four-way reversing valve D port → four-way reversing valve C port → outdoor heat exchanger → refrigerant pump inlet.

[0052] In this cycle, compressor 11 is completely shut down, and refrigerant pump 41 serves as the sole power source driving the refrigerant to circulate throughout the system. Electronic expansion valve 14 is fully open, minimizing flow resistance and increasing refrigerant circulation speed. Electric heating device 44 uniformly heats the refrigerant circulating through gas-liquid separator 15, gradually vaporizing the liquid refrigerant. As the preheating process progresses, the refrigerant temperature within the system gradually increases, and the pressure on the low-pressure side of the system also gradually rises.

[0053] The controller is further configured to: after controlling the air conditioner to enter the circulating preheating mode, acquire the system low-pressure side pressure Ps in real time through the low-pressure pressure sensor 453, acquire the compressor exhaust temperature Td through the compressor exhaust temperature sensor 452, and pre-store the air conditioner circulating preheating completion judgment threshold conditions; the circulating preheating completion judgment threshold conditions include: the system low-pressure side pressure Ps reaches the preset low-pressure pressure threshold Pso, and the compressor exhaust temperature Td reaches the preset exhaust temperature threshold Tdo; when the detected system low-pressure side pressure Ps and compressor exhaust temperature Td simultaneously meet the circulating preheating completion judgment threshold conditions, the preheating is judged to be completed, and the air conditioner is controlled to exit the circulating preheating mode.

[0054] See appendix Figure 4 The specific execution steps of the control logic corresponding to the above-mentioned cycle preheating completion determination are as follows: C1. The air conditioner enters the cycle preheating mode; C2. The controller obtains the system low-pressure side pressure Ps in real time through the low-pressure sensor 453; C3. The controller obtains the compressor discharge temperature Td in real time through the compressor discharge temperature sensor 452; C4. The controller determines whether the system low-pressure side pressure Ps has reached the preset low-pressure threshold Pso; C5. If the determination result of C4 is "yes", the controller further determines whether the compressor discharge temperature Td has reached the preset discharge temperature threshold Tdo; C6. If the determination result of C5 is "yes", the controller determines that preheating is complete and controls the air conditioner to exit the cycle preheating mode; C7. If the determination result of C4 or C5 is "no", the controller controls the air conditioner to continue to operate in the cycle preheating mode.

[0055] In this embodiment, the preset low-pressure threshold Pso and the preset exhaust temperature threshold Tdo are set according to the outdoor ambient temperature Ta in different ranges to adapt to the refrigerant vaporization characteristics under different low-temperature environments. Taking R410A refrigerant as an example, the specific parameters are shown in the table below:

[0056] By employing a dual-parameter approach of system pressure and exhaust temperature, and setting thresholds based on outdoor ambient temperature ranges, the degree of refrigerant vaporization can be more accurately determined under different low-temperature conditions. The system low-pressure side pressure reflects the overall degree of refrigerant vaporization within the system, while the compressor exhaust temperature reflects the refrigerant temperature at the compressor 11's suction port. Only when both parameters simultaneously reach the threshold of their respective ranges can it be ensured that the compressor 11 will not draw in liquid refrigerant during startup, fundamentally preventing liquid slugging.

[0057] The controller is further configured to: when the air conditioner exits the circulating preheating mode, first perform a preheating end transition operation: control the solenoid valve 42 to open, so that the refrigerant bypasses the refrigerant pump 41; control the four-way reversing valve 12 to de-energize (i.e., the cooling direction); control the electronic expansion valve 14 to close; control the refrigerant pump 41 to stop running; control the electric heating device 44 to stop running.

[0058] See appendix Figure 5 The specific execution steps corresponding to the above preheating end transition control logic are as follows: D1, the controller determines that preheating is complete; D2, the controller controls the solenoid valve 42 to open; D3, the controller controls the four-way reversing valve 12 to remain de-energized; D4, the controller controls the electronic expansion valve 14 to close; D5, the controller controls the refrigerant pump 41 to stop running; D6, the controller controls the electric heating device 44 to stop running; D7, the preheating end transition operation is completed.

[0059] In this embodiment, a dedicated preheating termination transition operation is set up to smoothly switch the refrigerant circulation loop and avoid sudden changes in system pressure that could impact various components. First, the solenoid valve 42 is opened, allowing the refrigerant to bypass the refrigerant pump 41, preparing for the pump's shutdown. Then, the electronic expansion valve 14 is closed, cutting off the refrigerant circulation loop. Finally, the refrigerant pump 41 and the electric heating device 44 are stopped. The entire transition process is carried out in an orderly manner, ensuring stable system pressure changes and improving the stability and reliability of system operation.

[0060] The controller is further configured to: after completing the preheating end transition operation, control the compressor 11 to start, simultaneously control the four-way reversing valve 12 to switch to the heating direction, control the electronic expansion valve 14 to switch to the heating dynamic adjustment mode, and the air conditioner enters the heating mode operation.

[0061] See appendix Figure 6 The specific execution steps corresponding to the heating mode switching control logic described above are as follows: E1, preheating end transition operation completed; E2, controller controls compressor 11 to start; E3, controller controls four-way reversing valve 12 to switch to heating direction; E4, controller controls electronic expansion valve 14 to switch to heating dynamic adjustment mode; E5, air conditioner enters heating mode operation. It should be noted that E2-E4 are control operations executed synchronously by the controller; the step numbers are only for clear illustration of all operations and do not represent the order of operations.

[0062] In this embodiment, after the compressor 11 starts, the four-way reversing valve 12 is immediately energized and switched to the heating direction, and the electronic expansion valve 14 switches to the heating dynamic adjustment mode, adjusting its opening in real time according to parameters such as indoor and outdoor ambient temperature and set temperature to control the refrigerant flow. See Appendix Figure 11At this time, the refrigerant circulation path is: compressor discharge port → four-way reversing valve D port → four-way reversing valve E port → indoor heat exchanger → electronic expansion valve → solenoid valve → outdoor heat exchanger → four-way reversing valve C port → four-way reversing valve S port → gas-liquid separator → compressor suction port.

[0063] By orderly switching the working status of each component, a seamless and smooth transition from the circulating preheating mode to the heating mode is achieved, ensuring a continuous and stable heating process and significantly shortening the user's waiting time for heating.

[0064] The controller is further configured to: after the air conditioner enters the circulating preheating mode, accumulate the running time of the circulating preheating mode in real time; when the accumulated running time of the circulating preheating mode reaches the preset maximum circulating preheating time threshold, but still does not meet the threshold condition for determining the completion of circulating preheating, control the air conditioner to exit the circulating preheating mode and trigger a preheating abnormality fault prompt.

[0065] Meanwhile, the controller is also configured to: if a user's command to exit preheating is received during the operation of the circulating preheating mode, the controller will immediately control the air conditioner to perform a preheating end transition operation and then switch to heating mode operation.

[0066] See appendix Figure 7 The specific execution steps corresponding to the above-mentioned abnormal protection and manual control logic are as follows: F1, the air conditioner enters the circulating preheating mode; F2, the controller accumulates the running time of the circulating preheating mode in real time and detects user input commands in real time; F3, the controller determines whether it has received a user's command to exit preheating; F4, if the result of F3 is "yes", the controller controls the air conditioner to perform a preheating end transition operation and then switches to heating mode; F5, if the result of F3 is "no", the controller determines whether the accumulated running time has reached the preset maximum circulating preheating time threshold; F6, if the result of F5 is "yes", the controller further determines whether the circulating preheating completion judgment threshold condition is met; F7, if the result of F6 is "no", the controller controls the air conditioner to exit the circulating preheating mode and triggers a preheating abnormality fault prompt; F8, if the result of F6 is "yes", the controller controls the air conditioner to perform a preheating end transition operation and then switches to heating mode.

[0067] In this embodiment, the preset maximum preheating cycle time threshold can be flexibly set according to the actual situation such as the heating capacity of the air conditioner and the usage environment. For example, it can be set to 1 hour. Setting a maximum preheating time protection mechanism can prevent the system from being unable to exit the preheating mode for a long time, and prevent excessive energy consumption and component damage caused by prolonged operation of the refrigerant pump 41 and electric heating device 44. At the same time, the fault prompts can promptly inform the user of abnormal system status, facilitating timely maintenance and repair.

[0068] Adding a manual exit function allows users to meet their urgent heating needs and improve user experience. When users urgently need heating, they can manually exit the preheating mode at any time and directly enter normal heating operation.

[0069] The controller is further configured to: when the air conditioner enters the circulating preheating mode, control the refrigerant pump 41 to start operating at a preset initial operating frequency Hzo_start; during the operation of the circulating preheating mode, calculate and adjust the operating frequency of the refrigerant pump 41 once every preset adjustment cycle; the calculation and adjustment method of the refrigerant pump operating frequency is: based on the current system low-pressure side pressure Ps(n) and the previous system low-pressure side pressure Ps(n-1), calculate the current pressure deviation value ΔPs(n) and the previous pressure deviation value ΔPs(n-1), respectively. n-1); Based on the preset proportional coefficient Kp, preset integral coefficient Ki, current pressure deviation value △Ps(n) and previous pressure deviation value △Ps(n-1), the current fluorine pump operating frequency adjustment amount △Hzo is calculated; Based on the previous fluorine pump operating frequency Hzo(n-1) and the current frequency adjustment amount △Hzo, the current fluorine pump operating frequency Hzo(n) is calculated; The calculated Hzo(n) is limited to control the operating frequency of fluorine pump 41 between the preset lower limit threshold and the preset upper limit threshold of fluorine pump frequency.

[0070] See appendix Figure 8 The specific execution steps corresponding to the above-mentioned refrigerant pump frequency conversion regulation control logic are as follows: G1. The controller controls the air conditioner to enter the circulating preheating mode; G2. The controller selects the corresponding preset initial operating frequency Hzo_start according to the current outdoor ambient temperature Ta, and controls the refrigerant pump 41 to start running at this frequency; G3. The controller obtains the system low-pressure side pressure Ps(n) detected this time and the system low-pressure side pressure Ps(n-1) detected last time every preset adjustment cycle; G4. The controller calculates the current pressure deviation value ΔPs(n) = Ps(n) - Pso and the previous pressure deviation value ΔPs(n-1) = Ps(n-1) - Pso; G5. The controller calculates the current refrigerant pump operation... The frequency adjustment amount ΔHzo = Kp × [ΔPs(n) - ΔPs(n-1)] + Ki × ΔPs(n); G6, the controller calculates the operating frequency of the fluorine pump this time Hzo(n) = Hzo(n-1) + ΔHzo; G7, the controller determines whether the calculated Hzo(n) is within the preset fluorine pump frequency range; G8, if Hzo(n) is within the preset fluorine pump frequency range, the controller controls the fluorine pump to run at the operating frequency Hzo(n) calculated this time; G9, if Hzo(n) exceeds the preset fluorine pump frequency range, the controller controls the fluorine pump 41 to run at the lower or upper limit threshold of the preset fluorine pump frequency range; G10, repeat steps G3 to G9 until preheating is completed.

[0071] Specifically, in step G9, if Hzo(n) is lower than the lower threshold of the preset fluorine pump frequency range, the fluorine pump 41 is controlled to operate according to the lower threshold; if Hzo(n) is higher than the upper threshold of the preset fluorine pump frequency range, the fluorine pump 41 is controlled to operate according to the upper threshold.

[0072] In this embodiment, the preset initial operating frequency Hzo_start is set according to the outdoor ambient temperature Ta interval to adapt to the refrigerant circulation requirements under different low-temperature environments. Taking R410A refrigerant as an example, the specific parameters are shown in the table below:

[0073] The preset adjustment cycle is exemplarily set to 1 minute, the preset proportional coefficient Kp is exemplarily set to 5, the preset integral coefficient Ki is exemplarily set to 1, the preset lower limit threshold of the refrigerant pump frequency is exemplarily set to 15Hz, and the preset upper limit threshold of the refrigerant pump frequency is exemplarily set to 60Hz.

[0074] The operating frequency of the refrigerant pump 41 is dynamically adjusted using a proportional-integral (PI) control algorithm, with initial frequencies set in intervals based on outdoor ambient temperature. This allows for real-time adjustment of the refrigerant circulation speed according to system pressure changes and ambient temperature. When the system pressure is low, the operating frequency of the refrigerant pump 41 is increased to accelerate refrigerant circulation and improve preheating efficiency. When the system pressure approaches the preset low-pressure threshold Pso, the operating frequency of the refrigerant pump 41 is decreased to prevent the system pressure from rising too quickly and ensure a smooth preheating process. This variable frequency control method improves preheating efficiency while ensuring system operational stability.

[0075] The technical solution of this embodiment can be adapted to the heating start-up requirements of air conditioners under different low-temperature environments. The following describes the specific control process in detail under three typical operating conditions: -25℃ extremely low temperature environment, -15℃ low temperature environment, and 0℃ critical low temperature environment, further demonstrating the versatility and accuracy of this technical solution. The control logic not mentioned under each operating condition follows the basic settings of the aforementioned embodiment.

[0076] (I) Operating conditions in extremely low temperature environments of -25℃ In an extremely low temperature environment of -25℃, after the air conditioner has been shut down for a long time, almost all the refrigerant in the system has liquefied and deposited at the bottom of the outdoor heat exchanger 13 and the gas-liquid separator 15. The pressure on the low-pressure side of the system is extremely low, and the compressor discharge temperature is also extremely low. At this time, sufficient preheating is required before the compressor 11 can be started.

[0077] When the user sends the heating start command, the controller obtains the outdoor ambient temperature Ta=-25℃ and the compressor discharge temperature Td=-28℃, both of which meet the low temperature start conditions (Tao=5℃, Tdo=0℃), so it controls the air conditioner to enter the circulation preheating mode.

[0078] Upon entering the circulating preheating mode, the controller synchronously executes the following linkage control operations: solenoid valve 42 closes, four-way reversing valve 12 is de-energized, electronic expansion valve 14 is fully open, refrigerant pump 41 starts operating at an initial frequency of 50Hz (corresponding to the Ta≤-20℃ range), and electric heating device 44 is activated. At this time, refrigerant pump 41 drives the refrigerant to circulate within the system, and electric heating device 44 heats the refrigerant circulating through gas-liquid separator 15.

[0079] During the preheating process, the controller adjusts the operating frequency of the refrigerant pump 41 every minute. Initially, the system's low-pressure side pressure Ps is very low, and the pressure deviation ΔPs is large, so the operating frequency of the refrigerant pump 41 rises rapidly until it reaches the upper limit of 60Hz. As preheating progresses, the refrigerant gradually vaporizes, the system's low-pressure side pressure Ps gradually rises, the pressure deviation ΔPs gradually decreases, and the operating frequency of the refrigerant pump 41 gradually decreases.

[0080] When the preheating has been running for a certain period of time (less than the preset maximum cycle preheating time threshold, for example, 55 minutes), the system low-pressure side pressure Ps reaches 0.6MPa and the compressor exhaust temperature Td reaches 8℃, which meets the cycle preheating completion judgment threshold conditions for this temperature range (Pso=0.6MPa, Tdo=8℃), and the controller determines that the preheating is complete.

[0081] Subsequently, the controller performs a preheating end transition operation: solenoid valve 42 opens, electronic expansion valve 14 closes, refrigerant pump 41 stops running, and electric heating device 44 stops running. After the transition operation is completed, the controller controls compressor 11 to start, and simultaneously controls four-way reversing valve 12 to switch to heating direction, electronic expansion valve 14 switches to heating dynamic adjustment mode, and the air conditioner enters heating mode operation.

[0082] The entire preheating process was smooth and efficient. No liquid slugging occurred when the compressor 11 started, and the user's waiting time was significantly reduced.

[0083] (II) Operating conditions in low-temperature environments of -15℃ At a low temperature of -15℃, most of the refrigerant in the system liquefies, and the low-pressure side pressure and compressor discharge temperature are slightly higher than at -25℃, requiring a relatively shorter preheating time.

[0084] When the user sends a heating start command, the controller obtains the outdoor ambient temperature Ta=-15℃ and the compressor discharge temperature Td=-18℃, which meets the low temperature start conditions, and then controls the air conditioner to enter the circulation preheating mode.

[0085] After entering the circulating preheating mode, the refrigerant pump 41 starts operating at an initial frequency of 40Hz (corresponding to the range of -20℃ < Ta ≤ -10℃). Since the initial system pressure is higher than that in the -25℃ environment, the pressure deviation value △Ps is relatively small. Therefore, the operating frequency of the refrigerant pump 41 increases slowly, reaching a maximum of about 55Hz.

[0086] When the preheating process lasts for a certain period of time (less than the preset maximum cycle preheating time threshold, such as 35 minutes), the system low-pressure side pressure Ps reaches 0.8MPa and the compressor exhaust temperature Td reaches 15℃, which meets the cycle preheating completion judgment threshold conditions for this temperature range (Pso=0.8MPa, Tdo=15℃), and the controller determines that the preheating is complete.

[0087] Subsequently, the controller performs a preheating end transition operation and controls the air conditioner to switch to heating mode. The entire preheating process is smooth and orderly, the compressor 11 starts safely and reliably, and the heating response is rapid.

[0088] (III) 0℃ Critical Low Temperature Environment Conditions At the critical low temperature of 0℃, only a small amount of refrigerant in the system liquefies, the low-pressure side pressure and compressor discharge temperature are relatively high, and the required preheating time is very short.

[0089] When the user sends a heating start command, the controller obtains the outdoor ambient temperature Ta=0℃ and the compressor discharge temperature Td=-3℃, which meets the low temperature start conditions, and then controls the air conditioner to enter the circulation preheating mode.

[0090] After entering the circulating preheating mode, the refrigerant pump 41 starts operating at an initial frequency of 25Hz (corresponding to the range of -10℃ < Ta ≤ 5℃). Due to the high initial system pressure and the small pressure deviation value ΔPs, the operating frequency of the refrigerant pump 41 remains at around 25Hz without significant increase.

[0091] When the preheating has been in progress for a certain period of time (less than the preset maximum cycle preheating time threshold, for example, 12 minutes), the system low-pressure side pressure Ps reaches 1.1 MPa and the compressor exhaust temperature Td reaches 25℃, which meets the cycle preheating completion judgment threshold conditions for this temperature range (Pso=1.1MPa, Tdo=25℃), and the controller determines that the preheating is complete.

[0092] Subsequently, the controller performs a preheating end transition operation and switches the air conditioner to heating mode. The entire preheating process is fast and efficient, avoiding both the risk of liquid slugging and unnecessary energy waste.

[0093] (iv) Abnormal preheating conditions During the preheating process, if abnormal situations such as refrigerant pump 41 failure, electric heating device 44 failure, or refrigerant leakage occur, the system low-pressure side pressure and compressor discharge temperature will not be able to reach the preset threshold. At this time, the maximum preheating time protection mechanism will come into play.

[0094] When the cumulative running time of the cyclic preheating mode reaches 1 hour (the preset maximum cyclic preheating time threshold), the system low-pressure side pressure Ps is still only 0.3MPa and the compressor exhaust temperature Td is still only -2℃. The cyclic preheating completion judgment threshold condition for the corresponding temperature range is not met, and the controller judges the preheating to be abnormal.

[0095] Therefore, the controller controls the air conditioner to exit the circulating preheating mode, shuts off the refrigerant pump 41 and the electric heating device 44, and sends a preheating abnormality fault prompt to the user through the air conditioner's display panel or mobile APP, reminding the user to contact maintenance personnel for repair in time.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0097] For ease of explanation, the above description has been provided in conjunction with specific embodiments. However, the above exemplary discussion is not intended to be exhaustive or to limit the embodiments to the specific forms disclosed above. Various modifications and variations can be obtained based on the above teachings. The selection and description of the above embodiments are for the purpose of better explaining the principles and practical applications, thereby enabling those skilled in the art to better utilize the described embodiments and various different variations of embodiments suitable for specific use considerations.

Claims

1. An air conditioner, characterized in that, The air conditioner has a circulating preheating mode, and the air conditioner includes: The outdoor unit is used for heat exchange with the outdoor environment. The outdoor unit is equipped with a compressor, a four-way reversing valve, an outdoor heat exchanger, an electronic expansion valve, and a gas-liquid separator. An indoor unit is used to exchange heat with indoor air in order to regulate the indoor air and achieve cooling or heating. The indoor unit is equipped with an indoor heat exchanger. The refrigerant circulation pipeline connects the outdoor unit and the indoor unit, so that the compressor, four-way reversing valve, indoor heat exchanger, electronic expansion valve, outdoor heat exchanger and gas-liquid separator are connected in sequence to form a closed refrigerant circulation loop. A refrigerant pump, connected in series in the refrigerant circulation pipeline between the outdoor heat exchanger and the electronic expansion valve, is used to drive the refrigerant to circulate in the refrigerant circulation loop in the circulation preheating mode. A solenoid valve is connected in parallel between the inlet and outlet of the fluorine pump; A one-way valve is connected in parallel between the suction port and the discharge port of the compressor. The one-way valve is directed from the suction port of the compressor to the discharge port. It is used to allow the refrigerant to flow through and bypass the compressor in the circulating preheating mode. An electric heating device is wound around the outer wall of the gas-liquid separator to preheat the refrigerant circulating through the gas-liquid separator; In the circulating preheating mode, the solenoid valve is closed, the one-way valve is open, the electric heating device is turned on, and the refrigerant pump drives the refrigerant to circulate in the refrigerant circulation loop and preheat the circulating refrigerant.

2. The air conditioner according to claim 1, characterized in that, It also includes detection components, which include an outdoor ambient temperature sensor, a compressor exhaust temperature sensor, and a low-pressure sensor. The outdoor ambient temperature sensor is located on the casing of the outdoor unit and is used to detect the outdoor ambient temperature where the air conditioner is located. The compressor exhaust temperature sensor is located at the exhaust port of the compressor and is used to detect the exhaust temperature of the compressor. The low-pressure sensor is located on the inlet pipe of the gas-liquid separator and is used to detect the low-pressure side pressure of the air conditioner's refrigerant circulation loop.

3. The air conditioner according to claim 2, characterized in that, It also includes a controller, which is configured to: upon receiving a heating start command, determine whether the air conditioner meets the low-temperature start conditions; if so, control the air conditioner to enter the circulating preheating mode; if not, control the air conditioner to enter the heating mode.

4. The air conditioner according to claim 3, characterized in that, The controller is further configured to: Obtain the outdoor ambient temperature Ta and the compressor exhaust temperature Td, and preset the low-temperature start-up threshold conditions for the air conditioner. The low-temperature start-up determination threshold conditions include: the outdoor ambient temperature Ta reaches the preset low-temperature start-up upper limit temperature threshold Tao, and the compressor exhaust temperature Td reaches the preset low-temperature start-up exhaust temperature threshold Tdo. When the detected outdoor ambient temperature Ta and the compressor exhaust temperature Td simultaneously meet the low-temperature start-up threshold condition, the air conditioner is determined to meet the low-temperature start-up condition. If either the detected outdoor ambient temperature Ta or the compressor exhaust temperature Td does not meet the low-temperature start-up threshold condition, the air conditioner is determined not to meet the low-temperature start-up condition.

5. The air conditioner according to claim 3, characterized in that, The controller is further configured to: When the air conditioner enters the circulating preheating mode, the following operations are performed: control the solenoid valve to close, control the four-way reversing valve to de-energize, control the electronic expansion valve to fully open, control the refrigerant pump to start running, and control the electric heating device to turn on.

6. The air conditioner according to claim 3, characterized in that, The controller is further configured to: When the air conditioner enters the circulating preheating mode, the refrigerant pump is controlled to start running at a preset initial operating frequency; During operation in the circulating preheating mode, the operating frequency of the fluorine pump is calculated and adjusted every preset adjustment cycle; The calculation and adjustment method for the operating frequency of the fluorine pump is as follows: based on the system low-pressure side pressure Ps(n) detected this time and the system low-pressure side pressure Ps(n-1) detected last time, calculate the pressure deviation value ΔPs(n) for this time and the pressure deviation value ΔPs(n-1) for the last time respectively. Based on the preset proportional coefficient Kp, the preset integral coefficient Ki, the current pressure deviation value △Ps(n) and the previous pressure deviation value △Ps(n-1), the frequency adjustment amount △Hzo of the current fluorine pump operation is calculated. Based on the previous operating frequency of the fluorine pump Hzo(n-1) and the current frequency adjustment ΔHzo, the current operating frequency of the fluorine pump Hzo(n) is calculated. Control the fluorine pump to operate at the calculated operating frequency Hzo(n), and control the operating frequency of the fluorine pump to be within the preset fluorine pump frequency range.

7. The air conditioner according to claim 3, characterized in that, The controller is further configured to: After the air conditioner enters the circulating preheating mode, the system low-pressure side pressure Ps and compressor exhaust temperature Td are obtained in real time, and the threshold conditions for determining the completion of the air conditioner's circulating preheating are preset. The threshold conditions for determining the completion of the cycle preheating include: the system low-pressure side pressure Ps reaches the preset low-pressure threshold Pso, and the compressor exhaust temperature Td reaches the preset exhaust temperature threshold Tdo. When the detected system low-pressure side pressure Ps and compressor exhaust temperature Td simultaneously meet the threshold conditions for completing the cycle preheating, the preheating is determined to be complete, and the air conditioner is controlled to exit the cycle preheating mode.

8. The air conditioner according to claim 7, characterized in that, The controller is further configured to: When the air conditioner exits the circulating preheating mode, a preheating end transition operation is first performed: the solenoid valve is opened, the four-way reversing valve is de-energized, the electronic expansion valve is closed, the refrigerant pump stops running, and the electric heating device is turned off.

9. The air conditioner according to claim 8, characterized in that, The controller is further configured to: After the preheating transition is completed, the compressor is started, and the four-way reversing valve is powered on to switch to the heating direction. The electronic expansion valve is switched to the heating dynamic adjustment mode, and the air conditioner enters the heating mode.

10. The air conditioner according to claim 7, characterized in that, The controller is further configured to: After the air conditioner enters the circulating preheating mode, the running time of the circulating preheating mode is accumulated in real time. When the cumulative running time of the cyclic preheating mode reaches the preset maximum cyclic preheating time threshold, but the cyclic preheating completion judgment threshold condition is still not met, the air conditioner is controlled to exit the cyclic preheating mode and a preheating abnormality fault prompt is triggered.

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