A multi-split air conditioner

Abstract

The application discloses a multi-connected air conditioner, which comprises an outdoor unit, a plurality of indoor units, an indoor heat exchanger, an indoor electronic expansion valve, an inlet temperature sensor, a bend temperature sensor, an indoor temperature sensor, and an indoor controller. The indoor heat exchanger is connected with the outdoor unit through the indoor electronic expansion valve. The indoor heat exchanger comprises an inlet and a plurality of bends. The indoor unit further comprises an indoor controller, an inlet temperature sensor, a bend temperature sensor, and an indoor temperature sensor. The inlet temperature sensor and the bend temperature sensor are arranged at the inlet and one of the bends respectively, and are used for detecting the inlet temperature and the bend temperature. The indoor temperature sensor is used for detecting the indoor temperature and transmitting the indoor temperature to the indoor controller. The indoor controller is configured to judge whether the indoor electronic expansion valve is in a limit small opening state according to the inlet temperature, the bend temperature, and the indoor temperature. If yes, the indoor controller controls the indoor electronic expansion valve to increase the opening degree. If no, the indoor controller keeps performing the overheating control. The application detects and controls the opening state of the indoor electronic expansion valve, and prevents the indoor unit from having no cooling effect.

Description

Technical Field

[0001] This invention relates to the field of air conditioning technology, and more specifically to a multi-connection air conditioner. Background Technology

[0002] In traditional indoor unit expansion valve control, the degree of throttling is adjusted by increasing or decreasing the opening of the expansion valve during cooling. As the amount of control increases, the resulting switching errors also increase. This can lead to situations where the indoor unit expansion valve fails to reset its opening accurately due to prolonged control, resulting in low temperature control efficiency and impacting the user experience. Furthermore, when the indoor unit expansion valve opening is too small, it may even close to zero or a very small opening, causing the indoor unit to lose its cooling capacity and severely affecting the user experience.

[0003] Existing technologies determine whether there is an error in the opening of the outdoor electronic expansion valve by measuring the compressor's target exhaust temperature, exhaust time, and operating frequency. If an error is found, the air conditioning system is restarted to reset the outdoor electronic expansion valve. This not only affects user experience but also only addresses the detection and elimination of errors in the outdoor electronic expansion valve, failing to address the detection and elimination of errors in the electronic expansion valves of one or more indoor units in a multi-split system.

[0004] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0005] In response to the problems mentioned in the background art, the present invention detects the opening status of the electronic expansion valve of the indoor unit of a multi-split air conditioner and adopts corresponding control strategies based on the detection results to avoid ineffective cooling of the indoor unit, improve the reliability of the whole unit operation, and enhance the user experience.

[0006] To achieve the above-mentioned objectives, the present invention employs the following technical solution:

[0007] In some embodiments of this application, a multi-split air conditioner is provided, including an outdoor unit and multiple indoor units; each indoor unit includes an indoor heat exchanger and an indoor electronic expansion valve; the indoor heat exchanger is connected to the outdoor unit through the indoor electronic expansion valve; the indoor heat exchanger includes an inlet, an outlet, and multiple elbows;

[0008] The indoor unit also includes an indoor unit controller and an inlet temperature sensor, an elbow temperature sensor, and an indoor temperature sensor, which are respectively connected to the indoor unit controller. The inlet temperature sensor and the elbow temperature sensor are respectively located at the inlet and one of the elbows, and are used to detect the inlet temperature and the elbow temperature and transmit them to the indoor unit controller. The indoor temperature sensor is used to detect the indoor temperature and transmit it to the indoor unit controller.

[0009] The indoor unit controller is configured to determine whether the indoor unit electronic expansion valve is in a minimum opening state based on the inlet temperature, the elbow temperature, and the indoor temperature; and when the indoor unit electronic expansion valve is in a minimum opening state, control it to increase the opening; and when the indoor unit electronic expansion valve is not in the minimum opening state, maintain superheat control.

[0010] In one specific embodiment, it also includes a suction superheat acquisition device and a pressure sensor, which are installed on the outdoor unit and connected to the indoor unit controller, respectively, for acquiring the suction superheat and low pressure of the outdoor unit and transmitting them to the indoor unit controller;

[0011] The indoor unit controller is configured with a first temperature limit, a second temperature limit, a first opening limit, a first low pressure limit, and a first duration, and is configured to determine whether the opening of the indoor unit's electronic expansion valve is lower than the first opening limit, whether the low pressure is lower than the first low pressure limit, and whether the difference between the inlet temperature and the suction superheat exceeds the first temperature limit for the first duration, or the difference between the elbow temperature and the suction superheat exceeds the first temperature limit for the first duration, or the difference between the indoor temperature and the second temperature limit does not exceed the inlet temperature for the first duration, or the difference between the indoor temperature and the second temperature limit does not exceed the elbow temperature for the first duration.

[0012] When all of the above conditions are met, the indoor unit electronic expansion valve is determined to be in the minimum opening state; otherwise, it is not in the minimum opening state.

[0013] In one specific embodiment, the indoor unit controller is further configured with an operating time limit and is configured to accumulate the duration of the cooling cycle temperature control mode. It determines whether the duration of the cooling cycle temperature control mode reaches or exceeds the operating time limit. If so, it determines whether the indoor unit electronic expansion valve is in the minimum opening state.

[0014] In one specific embodiment, the indoor unit controller is configured to terminate the increased opening degree control if the indoor unit ends its cooling cycle when the increased opening degree control is executed;

[0015] When the indoor unit ends the cooling cycle or switches to another operating mode, the duration of the cooling cycle temperature control mode is reset to zero.

[0016] In some specific embodiments, the indoor unit controller is configured with an increased opening degree, a minimum opening degree, a second opening degree limit, and a third temperature limit; the initial value of the minimum opening degree is 0; the second opening degree limit is greater than the first opening degree limit; the increased opening degree control includes:

[0017] Determine whether the minimum opening degree is 0; when it is 0, control the indoor unit's electronic expansion valve to close.

[0018] After the indoor unit electronic expansion valve is closed, the opening degree of the indoor unit electronic expansion valve is increased at least once by the increased opening degree; after each increase in the increased opening degree, it is determined whether the opening degree of the indoor unit electronic expansion valve exceeds the second opening degree limit; if yes, the indoor unit electronic expansion valve is controlled to restore the superheat control; if no, it is determined whether the difference between the elbow temperature before the increase in the increased opening degree and the elbow temperature after the increase in the increased opening degree exceeds the third temperature limit, or whether the difference between the inlet temperature before the increase in the increased opening degree and the inlet temperature after the increase in the increased opening degree exceeds the third temperature limit, and if yes, it is determined that the indoor unit electronic expansion valve is open, and minimum opening degree storage control and superheat control are restored; if no, the indoor unit electronic expansion valve is controlled to continue to increase the increased opening degree.

[0019] In some specific embodiments, the minimum opening degree storage control includes:

[0020] Determine whether the low pressure is lower than the first low pressure limit;

[0021] If yes, then determine whether the current opening degree of the indoor unit electronic expansion valve exceeds the first opening degree limit. If yes, the first opening degree limit is stored to the minimum opening degree and the superheat control is restored. If no, the current opening degree of the indoor unit electronic expansion valve is stored to the minimum opening degree and the superheat control is restored.

[0022] If not, then directly restore the superheat control.

[0023] In some specific embodiments, the increase in opening control further includes:

[0024] Determine whether the minimum opening degree is 0; if it is not 0, control the indoor unit's electronic expansion valve to open to the minimum opening degree;

[0025] After the indoor unit electronic expansion valve is opened to the minimum opening degree, the opening degree of the indoor unit electronic expansion valve is increased at least once by the increased opening degree; after each increase in the increased opening degree, it is determined whether the opening degree of the indoor unit electronic expansion valve exceeds the second opening degree limit; if yes, the indoor unit electronic expansion valve is controlled to restore the superheat control; if no, it is determined whether the difference between the elbow temperature before the increase in the increased opening degree and the elbow temperature after the increase in the increased opening degree exceeds the third temperature limit or whether the difference between the inlet temperature before the increase in the increased opening degree and the inlet temperature after the increase in the increased opening degree exceeds the third temperature limit. If yes, it is determined that the indoor unit electronic expansion valve is open and the superheat control is restored; if no, the indoor unit electronic expansion valve is closed, and a confirmation judgment and control are performed.

[0026] In some specific embodiments, the indoor unit electronic expansion valve closure confirmation judgment and control includes:

[0027] Determine whether the difference between the indoor temperature and the second temperature limit exceeds the inlet temperature, and whether the difference between the indoor temperature and the second temperature limit exceeds the elbow temperature;

[0028] If yes, the indoor unit's electronic expansion valve resumes the superheat control; if no, the opening of the indoor unit's electronic expansion valve continues to increase.

[0029] In some specific embodiments, the indoor unit controller is configured with a second pressure limit, which is less than the first pressure limit; the indoor unit controller is configured to determine whether the low pressure is lower than the second pressure limit when the indoor unit electronic expansion valve is in the minimum opening state; and when the low pressure is lower than the second pressure limit, control the opening of the indoor unit electronic expansion valve to increase to the second opening limit, and restore the superheat control.

[0030] In one specific embodiment, an outlet temperature sensor is also included, which is disposed at the outlet and connected to the indoor unit controller for detecting the outlet temperature and transmitting it to the indoor unit controller; the indoor unit controller is also configured with a superheat setting value; the superheat control is performed by using the difference between the outlet temperature and the inlet temperature and the superheat setting value to perform intake superheat PI control for controlling the opening degree of the indoor unit's electronic expansion valve.

[0031] Compared with the prior art, the advantages and positive effects of the present invention are:

[0032] The multi-split air conditioner of this invention collects the inlet temperature, elbow temperature, and indoor temperature of the indoor unit's heat exchanger to determine whether the indoor unit's electronic expansion valve is in a state of extreme minimum opening. Based on the determination, it performs control to increase the opening or maintain superheat control, preventing the problem that the indoor unit is in a cooling cycle but has no cooling effect due to the indoor unit's electronic expansion valve being in a state of extreme minimum opening caused by errors in temperature control adjustment of the indoor unit's electronic expansion valve during the multi-split air conditioner's cooling cycle. This improves the reliability of the multi-split air conditioner's cooling operation and enhances the user experience.

[0033] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0034] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of a system according to an embodiment;

[0036] Figure 2 This is a schematic diagram of the connection of the control components according to an embodiment;

[0037] Figure 3 This is a schematic diagram of the connection of the control components according to another embodiment;

[0038] Figure 4 This is a schematic diagram of the control flow according to an embodiment;

[0039] Figure 5 This is a schematic diagram of the control flow according to an embodiment;

[0040] Figure 6 This is a schematic diagram of the control flow for determination condition I according to an embodiment;

[0041] Figure 7 This is a schematic diagram of an indoor heat exchanger temperature acquisition process according to one embodiment;

[0042] Figure 8 This is a schematic diagram of an indoor heat exchanger temperature acquisition process according to another embodiment;

[0043] Figure 9 This is a schematic diagram of the control flow for determination condition II according to the embodiment;

[0044] Figure 10This is a schematic diagram of the control flow for determination condition III according to the embodiment;

[0045] Figure 11 This is a schematic diagram of the control flow for determination condition IV according to an embodiment.

[0046] Figure label:

[0047] 1. Indoor unit; 11. Indoor heat exchanger; 111. Inlet; 112. Elbow; 113. Outlet; 12. Indoor unit electronic expansion valve; 13. Indoor unit controller; 14. Inlet temperature sensor; 15. Elbow temperature sensor; 16. Indoor temperature sensor; 2. Outdoor unit; 21. Compressor; 22. Outdoor unit electronic expansion valve; 23. Pressure sensor; 24. Suction temperature sensor; 25. Outdoor unit controller. Implementation

[0048] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0049] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "multiple" means two or more.

[0050] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0051] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0052] Air conditioners execute a refrigeration cycle using a compressor, condenser, expansion valve, and evaporator. The refrigeration cycle involves a series of processes, including compression, condensation, expansion, and evaporation, to cool or heat an indoor space.

[0053] Low-temperature, low-pressure refrigerant enters the compressor, which compresses it into a high-temperature, high-pressure refrigerant gas and discharges the compressed refrigerant gas. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and the heat is released to the surrounding environment through the condensation process.

[0054] The expansion valve expands the high-temperature, high-pressure liquid refrigerant that condenses in the condenser into a low-pressure liquid refrigerant. The evaporator evaporates the expanded refrigerant in the expansion valve and returns the low-temperature, low-pressure refrigerant gas to the compressor. The evaporator achieves its cooling effect by utilizing the latent heat of refrigerant evaporation to exchange heat with the material being cooled. Throughout the cycle, the air conditioner regulates the temperature of the indoor space.

[0055] The outdoor unit of an air conditioner refers to the part of the refrigeration cycle that includes the compressor and the outdoor heat exchanger. The indoor unit of an air conditioner includes the indoor heat exchanger, and an expansion valve can be provided in either the indoor or outdoor unit.

[0056] The indoor and outdoor heat exchangers function as either condensers or evaporators. When the indoor heat exchanger is used as a condenser, the air conditioner functions as a heater in heating mode; when the indoor heat exchanger is used as an evaporator, the air conditioner functions as a cooler in cooling mode.

[0057] Reference Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11The multi-split air conditioner of the present invention includes multiple indoor units 1 and outdoor units 2; the outdoor unit 2 includes the compressor 21 and condenser described in the above air conditioner principle; the indoor unit 1 includes an indoor heat exchanger 11, which is equivalent to the evaporator in the above air conditioner; the expansion valve described in the above air conditioner principle includes multiple indoor unit electronic expansion valves 12 and outdoor unit electronic expansion valves 22 in this application.

[0058] Each indoor heat exchanger 11 of indoor unit 1 is connected to outdoor unit 2 through the corresponding indoor electronic expansion valve 12 of indoor unit 1; that is, each indoor heat exchanger 11 of indoor unit 1 is connected in series with the corresponding indoor electronic expansion valve 12 of indoor unit 1 and then connected to the same refrigerant pipe, and connected to the condenser of outdoor unit 2 through the refrigerant pipe; while the outdoor electronic expansion valve 22 is installed on the refrigerant pipe of outdoor unit 2 for refrigerant throttling; and each indoor electronic expansion valve 12 throttles the refrigerant entering each indoor heat exchanger 11 to ensure the cooling effect of each indoor unit 1, and adjusts the cooling effect of each indoor unit 1 by controlling the opening of each indoor electronic expansion valve 12.

[0059] The indoor heat exchanger 11 includes an inlet 111, an outlet 113, and multiple elbows 112. The indoor unit 1 also includes an indoor unit controller 13 and an inlet temperature sensor 14, an elbow temperature sensor 15, and an indoor temperature sensor 16, which are respectively connected to the indoor unit controller 13. The inlet temperature sensor 14 and the elbow temperature sensor 15 are respectively installed at the inlet 111 and one of the elbows 112 of the indoor heat exchanger 11, and are used to detect the inlet temperature and elbow temperature of the indoor heat exchanger 11 and transmit them to the indoor unit controller 13. The indoor temperature sensor 16 is used to detect the indoor temperature and transmit it to the indoor unit controller 13.

[0060] The indoor unit controller 13 is configured to determine whether the indoor unit electronic expansion valve 12 is in a minimum opening state based on the received inlet temperature, elbow temperature, and indoor temperature; and when it is determined that the indoor unit electronic expansion valve 12 is in a minimum opening state, it controls the indoor unit electronic expansion valve 12 to increase its opening; and when it is determined that the indoor unit electronic expansion valve 12 is not in a minimum opening state, it continues to perform superheat control on the opening of the indoor unit electronic expansion valve 12.

[0061] That is, during the refrigeration cycle, the indoor unit controller 13 of indoor unit 1 controls the superheat of the corresponding indoor unit electronic expansion valve 12. In other words, during the refrigeration cycle, the indoor unit controller 13 controls the opening of the indoor unit electronic expansion valve 12 based on the suction superheat of the outdoor unit 2, thereby achieving the cooling capacity used to adjust the temperature in the room. During the superheat control of the indoor unit electronic expansion valve 12, the controller receives the inlet temperature, elbow temperature, and indoor temperature of the corresponding indoor heat exchanger 11, and determines the state of the corresponding indoor unit electronic expansion valve 12 based on these temperatures. It determines whether the valve is in a minimum opening state, which is used to determine if there is an error in the opening control of the indoor unit electronic expansion valve 12, and whether the existing error has affected the cooling effect of the indoor unit 1. The determination based on the received inlet temperature, elbow temperature, and indoor temperature constitutes the judgment condition I; the minimum opening state is when the opening of the indoor unit electronic expansion valve 12 is small due to control error, and this opening state prevents the indoor unit 1 from cooling normally. When the indoor unit controller 13 determines that the indoor unit electronic expansion valve 12 is in the minimum opening state, it controls the corresponding indoor unit electronic expansion valve 12 to increase the opening degree, so that the opening degree of the indoor unit electronic expansion valve 12 increases; when the indoor unit controller 13 determines that the indoor unit electronic expansion valve 12 is not in the minimum opening state, it maintains the superheat control.

[0062] This invention relates to a multi-split air conditioner that collects the inlet temperature and elbow temperature of the indoor heat exchanger 11 of the corresponding indoor unit 1, as well as the indoor temperature of the corresponding indoor unit 1. It then uses these temperatures to determine whether the control error of the indoor unit's electronic expansion valve 12 has affected the cooling effect of the indoor unit 1. When the control error of the electronic expansion valve 12 does affect the cooling effect of the indoor unit 1, the invention controls the electronic expansion valve 12 to increase its opening degree, preventing a decrease in cooling effect due to the control error and improving the user experience. This invention ensures the accuracy of the temperature judgment at the inlet of the indoor heat exchanger 11 by cross-referencing or selectively judging the inlet temperature and elbow temperature, thereby improving the accuracy of the opening state judgment of the electronic expansion valve 12. Supplementary judgment using the indoor temperature further ensures the accuracy of the opening state judgment of the electronic expansion valve 12. Increasing the opening degree control ensures the cooling effect of the indoor unit 1, improves the reliability of the multi-split air conditioner operation, and enhances the user experience.

[0063] The control and principle of the multi-split air conditioner of the present invention will be described in detail below through specific embodiments.

[0064] In one specific embodiment, refer to Figure 1 , Figure 2 , Figure 3 , Figure 5 , Figure 6 The multi-split air conditioner also includes a suction superheat acquisition device and a pressure sensor 23, which are installed on the outdoor unit 2 and connected to the indoor unit controller 13 respectively. They are used to acquire the suction superheat and low pressure of the outdoor unit 2 and transmit them to the indoor unit controller 13.

[0065] The indoor unit controller 13 is configured with a first temperature limit, a second temperature limit, a first opening limit, a first low pressure limit, and a first duration. It is configured to determine whether the opening of the indoor unit electronic expansion valve 12 is lower than the first opening limit, whether the low pressure is lower than the first low pressure limit, and whether the difference between the inlet temperature and the suction superheat exceeds the first temperature limit for a first duration, or whether the difference between the elbow temperature and the suction superheat exceeds the first temperature limit for a first duration, or whether the difference between the indoor temperature and the second temperature limit does not exceed the inlet temperature for a first duration, or whether the difference between the indoor temperature and the second temperature limit does not exceed the elbow temperature for a first duration.

[0066] When the indoor unit controller 13 determines that all of the above conditions of the indoor unit 1 are met, it determines that the indoor unit electronic expansion valve 12 is in the minimum opening state; otherwise, it is not in the minimum opening state.

[0067] That is, when the indoor unit controller 13 determines that the opening degree of the indoor unit electronic expansion valve 12 does not exceed the first opening degree limit, and the low pressure does not exceed the first low pressure limit, and any one or more of the following four conditions are met: the difference between the inlet temperature and the suction superheat exceeds the first temperature limit for a first duration, the difference between the elbow temperature and the suction superheat exceeds the first temperature limit for a first duration, the difference between the indoor temperature and the second temperature limit does not exceed the inlet temperature for a first duration, and the difference between the indoor temperature and the second temperature limit does not exceed the elbow temperature for a first duration, the indoor unit electronic expansion valve 12 is determined to be in the minimum opening state. Otherwise, if the indoor unit controller 13 determines that the opening degree of the indoor unit electronic expansion valve 12 exceeds the first opening limit or the low pressure exceeds the first low pressure limit, or if either or both of these conditions are met, then the indoor unit electronic expansion valve 12 is determined not to be in the minimum opening state. Alternatively, if all four conditions are not met, the indoor unit electronic expansion valve 12 is also not in the minimum opening state.

[0068] The first opening limit is the minimum opening of the indoor unit's electronic expansion valve 12 when controlling overheating.

[0069] In this embodiment, the multi-split air conditioner determines the state of the indoor unit's electronic expansion valve 12 by comparing the difference between the inlet temperature, elbow temperature, and suction superheat with the set first temperature limit, and by supplementing the determination with the relationship between the indoor temperature and the inlet temperature, and the relationship between the indoor temperature and the elbow temperature. This makes the determination of the minimum opening state of the indoor unit's electronic expansion valve 12 more accurate and without omissions, ensuring the cooling effect of the indoor unit 1 and improving the user experience.

[0070] Of course, the indoor unit controller 13 can obtain the intake superheat and low pressure through the outdoor unit controller 25, which is connected to the indoor unit. That is, the outdoor unit 2 includes the outdoor unit controller 25, the intake superheat acquisition device, the pressure sensor 23, and each indoor unit controller 13, which are respectively connected to the outdoor unit controller 25; the outdoor unit controller 25 receives the intake superheat acquired by the intake superheat acquisition device and the low pressure measured by the pressure sensor 23, and transmits the received intake superheat and low pressure to the indoor unit controller 13.

[0071] In one specific embodiment, refer to Figure 4 , Figure 5 , Figure 6 The indoor unit controller 13 is also configured with an operating time limit, and is configured to accumulate the duration of the indoor unit 1's cooling cycle temperature control operation and determine whether the duration of the cooling cycle temperature control operation has reached the operating time limit; when it is, it determines whether the indoor unit's electronic expansion valve 12 is in the minimum opening state.

[0072] That is, the determination of whether there is a control error in the opening of the indoor unit's electronic expansion valve 12 and whether the control error affects the cooling effect is only made when the cumulative operating time of the multi-split unit's refrigeration cycle temperature control reaches or exceeds the operating time limit. The cumulative operating time of the refrigeration cycle temperature control is the operating duration of the refrigeration cycle mode, such as refrigeration mode or dehumidification mode, and is reset to zero when the operating mode is switched from the refrigeration cycle temperature control mode to other non-refrigeration cycle modes.

[0073] In other words, the accumulated temperature control operation time in both cooling and dehumidification modes is reset to zero when the operation mode is switched from cooling or dehumidification to other modes such as heating or ventilation.

[0074] In other words, the operating time without temperature control in cooling mode and dehumidification mode is not accumulated; that is, without temperature control in cooling mode or dehumidification mode, there is no control of the indoor unit electronic expansion valve 12, and no error is generated by the indoor unit electronic expansion valve 12.

[0075] This embodiment of the multi-split air conditioner specifies the cumulative duration of the refrigeration cycle temperature control operation, reduces invalid judgments, extends the judgment cycle and reduces the judgment frequency, reduces the occupation of software and hardware resources, and improves control efficiency.

[0076] In one specific embodiment, refer to Figure 5 , Figure 6 The opening state of the indoor unit's electronic expansion valve 12 is determined by whether judgment condition I is met (S2). Judgment condition I specifically includes the following steps:

[0077] S21. Determine whether the refrigeration cycle temperature control time has reached or exceeded the operating time limit; if so, proceed to the determination in S22.

[0078] S22. Determine whether the opening degree of the indoor unit's electronic expansion valve 12 has not exceeded the first opening degree limit. If so, proceed with the determination in S23.

[0079] S23. Determine whether the low pressure does not exceed the first low pressure limit; if not, proceed to the determination in S22; if yes, proceed to the determination in S24.

[0080] S24. Determine whether the difference between the inlet temperature and the intake superheat exceeds the first temperature limit for a first duration or whether the difference between the elbow temperature and the intake superheat exceeds the first temperature limit for a first duration. If yes, proceed to S3 to increase the opening control. If no, proceed to S25 to make the determination.

[0081] S25. Determine whether the difference between the indoor temperature and the second temperature limit does not exceed the first duration of the inlet temperature or whether the difference between the indoor temperature and the second temperature limit does not exceed the first duration of the elbow temperature. If yes, execute S3 to increase the opening control. If no, execute the judgment in S22.

[0082] In one specific embodiment, refer to Figure 4 , Figure 5 , Figure 6 The indoor unit controller 13 is configured to terminate the increased opening control when the indoor unit 1 finishes its cooling cycle. Specifically, when the indoor unit 1 determines that the electronic expansion valve 12 is at its minimum opening (S2) and performs increased opening control (S3), if the indoor unit 1 switches its cooling cycle to another cycle (S4), such as switching from cooling mode or dehumidification mode to heating mode or fan mode, the increased opening control is terminated (S5). At this time, the accumulated duration of the cooling cycle temperature control mode is also reset to zero (S6).

[0083] In some specific embodiments, refer to Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11The indoor unit controller 13 is configured with an increase in opening degree, a minimum opening degree, a delay time, a second opening degree limit, and a third temperature limit; the initial value of the minimum opening degree is set to 0; the second opening degree limit is greater than the first opening degree limit.

[0084] The increase opening control S3 includes the following steps:

[0085] S31. Determine if the minimum opening is 0; if the minimum opening is 0, execute S32.

[0086] S32, control the indoor unit's electronic expansion valve 12 to close to 0 degree; execute S33 after a stable delay time following the closure of the indoor unit's electronic expansion valve 12;

[0087] S33. Obtain the inlet temperature and elbow temperature, and store the obtained inlet temperature and elbow temperature;

[0088] S34. Increase the opening of the indoor unit's electronic expansion valve 12 by at least one step; and execute S35 after increasing the opening by one step.

[0089] S35. Determine whether the opening degree of the indoor unit's electronic expansion valve 12 exceeds the second opening degree limit;

[0090] If so, that is, if the opening degree of the indoor unit electronic expansion valve 12 reaches the second opening degree limit or above, then execute S7 to restore the opening degree control of the indoor unit electronic expansion valve 12 to superheat control.

[0091] If not, that is, if the opening degree of the indoor unit's electronic expansion valve 12 does not reach the second opening limit, then after a delay, the judgment condition II of S37 is executed; specifically,

[0092] S37. Determine whether the difference between the elbow temperature before and after increasing the opening exceeds the third temperature limit, or whether the difference between the inlet temperature before and after increasing the opening exceeds the third temperature limit; and if yes, determine that the indoor unit electronic expansion valve 12 is open, and execute the judgment of minimum opening storage judgment condition III in S38, minimum opening storage control in S1, and return to superheat control in S7; if no, continue to execute the control of the indoor unit electronic expansion valve 12 to increase the opening in S34.

[0093] In other words, when the opening of the indoor unit's electronic expansion valve 12 has not reached the second opening limit, the timing starts after the opening of the indoor unit's electronic expansion valve 12 is increased. When the timing reaches the delay time, the inlet temperature and elbow temperature are obtained, which are the inlet temperature and elbow temperature after the opening is increased. After the delay time, the inlet temperature and elbow temperature are more stable, which can better reflect the opening status of the indoor unit 1's electronic expansion valve after the opening is increased, thus improving accuracy and the accuracy of the judgment.

[0094] In this embodiment, when the indoor unit's electronic expansion valve 12 has a control error that affects the cooling effect, if the minimum opening degree does not have a stored non-zero value, the indoor unit's electronic expansion valve 12 is controlled to close to 0 opening degree for reset, and then gradually opened. The difference between the inlet temperature before and after increasing the opening degree or the elbow temperature difference is used to determine whether it has opened to the normal state, thus restoring its cooling effect and improving the reliability and accuracy of solving the problem of the indoor unit's electronic expansion valve 12 control error affecting the cooling effect.

[0095] In some specific embodiments, refer to Figure 7 To increase the opening control S3, follow these steps:

[0096] S32. When the minimum opening value is determined to be 0, the indoor unit electronic expansion valve 12 is closed.

[0097] S33. After the indoor unit's electronic expansion valve 12 closes, the inlet temperature and elbow temperature are acquired and stored after a delay.

[0098] S34. Increase the opening degree of the electronic expansion valve 12 of the indoor unit;

[0099] S35. Determine whether the opening degree of the indoor unit's electronic expansion valve 12 exceeds the second opening degree limit;

[0100] S36. After increasing the opening degree and delaying the time, obtain and store the inlet temperature and elbow temperature;

[0101] S37 Determine whether condition II is met.

[0102] In some specific embodiments, refer to Figure 9 The specific steps for determining condition II of S37 are as follows:

[0103] S371. Determine whether the difference between the elbow temperature before and after increasing the opening exceeds the third temperature limit. If yes, perform minimum opening storage control; otherwise, execute the judgment in S372.

[0104] S372. Determine whether the difference between the inlet temperature before increasing the opening degree and the inlet temperature after increasing the opening degree exceeds the third temperature limit; if yes, determine that the indoor unit electronic expansion valve 12 is open, and perform minimum opening degree storage control and return to superheat control S7; if no, continue to increase the opening degree control of the indoor unit electronic expansion valve 12.

[0105] In some specific embodiments, refer to Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 Minimum opening degree storage control includes:

[0106] S381. Determine whether the low-pressure level is lower than the first low-pressure limit.

[0107] If so, store the minimum opening degree; and if it is determined in S382 that the current opening degree of the indoor unit electronic expansion valve 12 exceeds the control minimum opening degree limit, execute S11 to store the first opening degree limit as the minimum opening degree and restore to superheat control S7; if it is determined in S382 that the current opening degree of the indoor unit electronic expansion valve 12 does not exceed the control minimum opening degree limit, execute S12 to store the current opening degree of the indoor unit electronic expansion valve 12 as the minimum opening degree and restore to superheat control S7.

[0108] If not, return directly to the superheat control S7.

[0109] In this embodiment, the minimum opening degree in the indoor unit controller 13 of the multi-split air conditioner is stored only once, and the non-zero stored value does not exceed the control minimum opening degree limit. The minimum opening degree value is determined according to the actual operating conditions to ensure that the indoor unit electronic expansion valve 12 will not stop cooling when the control error after storing the minimum opening degree is eliminated, thus ensuring the cooling effect of the indoor unit 1 and improving the error elimination efficiency.

[0110] In some specific embodiments, refer to Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 The increased opening control S3 also includes:

[0111] S31. Determine if the minimum opening is 0; if the minimum opening is non-zero, execute S320.

[0112] S320, controls the indoor unit's electronic expansion valve 12 to open to its minimum opening degree;

[0113] S33. After the indoor unit's electronic expansion valve 12 is closed, the inlet temperature and elbow temperature are obtained after a stable delay time, and the obtained inlet temperature and elbow temperature are stored.

[0114] S34. Increase the opening of the indoor unit electronic expansion valve 12 by at least one step; and after increasing the opening by one step, execute S35 to determine whether the opening of the indoor unit electronic expansion valve 12 exceeds the second opening limit.

[0115] If so, that is, the opening degree of the indoor unit electronic expansion valve 12 reaches the second opening degree limit or above, the opening degree control of the indoor unit electronic expansion valve 12 is restored to the superheat control S7.

[0116] If not, that is, the opening degree of the indoor unit electronic expansion valve 12 has not reached the second opening degree limit, then after the delay time, the judgment condition II is executed to determine whether it is met;

[0117] Specifically, it determines whether the difference between the elbow temperature before and after increasing the opening exceeds the third temperature limit, or whether the difference between the inlet temperature before and after increasing the opening exceeds the third temperature limit; and if yes, it determines that the indoor unit electronic expansion valve 12 is open and returns to the superheat control S7; if no, it performs the indoor unit electronic expansion valve 12 closure confirmation judgment and control S39.

[0118] The multi-split air conditioner in this embodiment improves the efficiency of eliminating control errors of the indoor unit's electronic expansion valve 12 by configuring a control method that increases the opening of the indoor unit's electronic expansion valve 12 when the non-zero minimum opening is met, thereby restoring the cooling effect of the indoor unit 1 as soon as possible and enhancing the user experience.

[0119] In some specific embodiments, refer to Figure 8 To increase the opening degree control, follow these steps:

[0120] S320. When the minimum opening degree is determined to be non-zero, the indoor unit electronic expansion valve 12 is reset to the minimum opening degree.

[0121] S33. After the indoor unit electronic expansion valve 12 is reset to the minimum opening, the inlet temperature and elbow temperature are acquired and stored after a delay time.

[0122] S34. Increase the opening degree of the electronic expansion valve 12 of the indoor unit;

[0123] S35. Determine whether the opening degree of the indoor unit's electronic expansion valve 12 exceeds the second opening degree limit;

[0124] S36. After increasing the opening degree and delaying the time, obtain and store the inlet temperature and elbow temperature;

[0125] S37 Determine whether condition II is met.

[0126] In some specific embodiments, refer to Figure 5 , Figure 11 The S39 indoor unit electronic expansion valve 12 closure confirmation judgment and control, i.e., judgment condition IV, includes:

[0127] S391. Determine whether the difference between the indoor temperature and the second temperature limit exceeds the inlet temperature, and S392. Determine whether the difference between the indoor temperature and the second temperature limit exceeds the elbow temperature.

[0128] If yes, the indoor unit electronic expansion valve 12 returns to the superheat control S7; if no, the indoor unit electronic expansion valve 12 is controlled to perform the next S34 to increase the opening degree.

[0129] When the increase in opening degree control ends, execute S6 to clear the running time limit.

[0130] In this embodiment, when the multi-split air conditioner determines that the indoor unit's electronic expansion valve 12 is in a closed state based on the changes in inlet temperature and elbow temperature, it further determines the opening state of the indoor unit's electronic expansion valve 12 by using the differences between the indoor temperature and the inlet temperature, and the differences between the indoor temperature and the elbow temperature. This more accurately determines the opening state of the indoor unit's electronic expansion valve 12, improves the accuracy and reliability of the determination of the indoor unit's electronic expansion valve 12 state, ensures the cooling effect of the indoor unit 1, and enhances the user experience.

[0131] In some specific embodiments, refer to Figure 5 , Figure 11 The S39 indoor unit electronic expansion valve 12 closure confirmation judgment and control, i.e., judgment condition IV, shall be carried out in accordance with the following steps:

[0132] S391. Determine whether the difference between the indoor temperature and the second temperature limit exceeds the inlet temperature. If yes, execute S392; otherwise, return to increase the opening control.

[0133] S392. Determine whether the difference between the indoor temperature and the second temperature limit exceeds the elbow temperature;

[0134] If yes, the indoor unit electronic expansion valve 12 returns to the superheat control S7; if no, the indoor unit electronic expansion valve 12 is controlled to execute the next round S34 to increase the opening degree.

[0135] In one specific embodiment, refer to Figure 7 , Figure 8 When the indoor unit's electronic expansion valve 12 is reset to the 0 opening value and the minimum non-zero opening value, a delay time is required to stabilize the indoor unit 1, especially to stabilize the inlet temperature and elbow temperature; and the inlet temperature and elbow temperature are obtained.

[0136] After the indoor unit electronic expansion valve 12 is increased in opening, a delay time is allowed to stabilize the system, inlet temperature, and elbow temperature after the indoor unit electronic expansion valve 12 is increased in opening, and the inlet temperature and elbow temperature are obtained.

[0137] In this embodiment, after the multi-split air conditioner is reset and the opening degree is increased, the inlet temperature and elbow temperature are obtained after a delay time, which improves the accuracy of the inlet temperature and elbow temperature, thereby improving the accuracy and reliability of the opening degree control of the indoor unit's electronic expansion valve 12.

[0138] In some specific embodiments, the indoor unit controller 13 is configured with a second pressure limit, which is less than the first pressure limit; the indoor unit controller 13 is configured to determine whether the low pressure is lower than the second pressure limit when the indoor unit electronic expansion valve 12 is in the minimum opening state; and when the low pressure is lower than the second pressure limit, control the opening of the indoor unit electronic expansion valve 12 to increase to the second opening limit in one go, and restore to superheat control.

[0139] In this embodiment, the multi-split air conditioner determines whether the low-pressure is below the second pressure limit. It confirms that the opening error of the electronic expansion valve of the indoor unit 1 has reached a level that affects the operation of the air conditioning system. Therefore, it controls the electronic expansion valve 12 of the indoor unit to increase to the control limit value at one time, so as to restore the low-pressure of the system as soon as possible, ensure the normal cooling of the entire multi-split air conditioner system, and improve the stability, reliability and cooling effect of the multi-split air conditioner.

[0140] In one specific embodiment, the superheat acquisition device includes a suction temperature sensor 24 and a second pressure sensor, which are respectively installed at the suction port of the compressor 21 and connected to the indoor unit controller 13 or the outdoor unit controller 25. They are used to detect the suction temperature and suction pressure and transmit them to the indoor unit controller 13 or the outdoor unit controller 25. The indoor unit controller 13 or the outdoor unit controller 25 calculates the suction superheat based on the suction temperature and suction pressure.

[0141] The intake temperature and intake pressure are transmitted to the outdoor unit controller 25. The outdoor unit controller 25 calculates the intake superheat based on the saturation temperature corresponding to the intake temperature minus the intake pressure, and transmits the data to the indoor unit controller 13.

[0142] In one specific embodiment, the indoor unit 1 further includes an outlet temperature sensor, which is installed at the outlet 113 of the indoor heat exchanger 11 and connected to the indoor unit controller 13, for detecting the outlet temperature and transmitting it to the indoor unit controller 13; the indoor unit controller 13 is also configured with a superheat setpoint and performs PI control on the indoor unit electronic expansion valve 12 based on the difference between the outlet temperature and the inlet temperature and the difference between the superheat setpoint.

[0143] Specifically, the deviation E(n) = [Tout(n) - Tin(n)] - SH;

[0144] The maximum value of the deviation E(n) is SH×2; when n in parentheses is 0, E(n) is 0.

[0145] SH is the superheat setpoint, i.e. the target superheat, which is set differently depending on the type of refrigerant and the different operating stages of the multi-split system;

[0146] Tout(n): The outlet temperature of the indoor heat exchanger 11 sampled for the nth time, which is the outlet temperature detected by the outlet temperature sensor.

[0147] Tin(n): The inlet temperature of the indoor heat exchanger 11 sampled for the nth time, which is the lower of the inlet temperature and the elbow temperature detected by the inlet temperature sensor 14 and the elbow temperature sensor.

[0148] The opening change value ΔP of the electronic expansion valve 12 of the indoor unit controlled by superheat is calculated by the following formula:

[0149] ΔP=Pfb(n)max / 100×{Kp×[ΔE(n)+ΔT / Ti×E(n)]}+G×[ANS(n)-ANS(n-1)];

[0150] ΔE(n)=E(n)-E(n-1);

[0151] In the formula,

[0152] The initial E(n-1) of the superheat control is 0.

[0153] Pfb(n)max is the maximum opening degree of the indoor unit's electronic expansion valve 12;

[0154] Kp is a proportional value, which is set according to the opening range of the indoor unit's electronic expansion valve 12 and the model. It increases as the opening range increases to prevent over-adjustment.

[0155] ΔT is the sampling time;

[0156] Ti is the integration time;

[0157] ΔT / Ti×E(n) is the variable for time integration;

[0158] G represents the model designation; different values ​​are assigned to models with different capacity ranges.

[0159] ANS(n) is the frequency feedback value of compressor 21. It feeds back the trend of compressor 21 frequency rising or falling to the indoor unit expansion valve, so that the control of the opening of indoor unit electronic expansion valve 12 takes into account the change in compressor 21 frequency and prevents over-control.

[0160] The multi-split air conditioner in this embodiment enables more precise control of the superheat of the indoor unit's electronic expansion valve 12, thereby finely controlling the indoor temperature.

[0161] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0162] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multi-split air conditioner, characterized in that, It includes an outdoor unit and multiple indoor units; each indoor unit includes an indoor heat exchanger and an indoor unit electronic expansion valve; the indoor heat exchanger is connected to the outdoor unit through the indoor unit electronic expansion valve; the indoor heat exchanger includes an inlet, an outlet, and multiple elbows; The indoor unit also includes an indoor unit controller and an inlet temperature sensor, an elbow temperature sensor, and an indoor temperature sensor, which are respectively connected to the indoor unit controller. The inlet temperature sensor and the elbow temperature sensor are respectively located at the inlet and one of the elbows, and are used to detect the inlet temperature and the elbow temperature and transmit them to the indoor unit controller. The indoor temperature sensor is used to detect the indoor temperature and transmit it to the indoor unit controller. The multi-split air conditioner also includes a superheat acquisition device and a pressure sensor. The superheat acquisition device and the pressure sensor are respectively installed on the outdoor unit and connected to the indoor unit controller. The superheat acquisition device is used to acquire the superheat of the outdoor unit's air intake and transmit it to the indoor unit controller. The pressure sensor is used to acquire the low pressure and transmit it to the indoor unit controller. The indoor unit controller is configured to determine whether the indoor unit electronic expansion valve is in a minimum opening state based on the inlet temperature, the elbow temperature, the indoor temperature, the outdoor unit suction superheat, and the low pressure. This includes: the indoor unit controller is configured with a first temperature limit, a second temperature limit, a first opening limit, a first low pressure limit, and a first duration; and is configured to determine whether the opening of the indoor unit electronic expansion valve is lower than the first opening limit, whether the low pressure is lower than the first low pressure limit, and whether the difference between the inlet temperature and the suction superheat exceeds the first temperature limit for the first duration, or whether the difference between the elbow temperature and the suction superheat exceeds the first temperature limit for the first duration, or whether the difference between the indoor temperature and the second temperature limit does not exceed the inlet temperature for the first duration, or whether the difference between the indoor temperature and the second temperature limit does not exceed the elbow temperature for the first duration. When all of the above conditions are met, the indoor unit electronic expansion valve is determined to be in the minimum opening state; otherwise, it is not in the minimum opening state. When the indoor unit's electronic expansion valve is at its minimum opening, it is controlled to increase its opening; when the indoor unit's electronic expansion valve is not at its minimum opening, superheat control is maintained.

2. The multi-split air conditioner according to claim 1, characterized in that, The indoor unit controller is also configured with an operating time limit and is configured to accumulate the duration of the cooling cycle temperature control mode. It determines whether the duration of the cooling cycle temperature control mode reaches or exceeds the operating time limit. If so, it determines whether the indoor unit electronic expansion valve is in the minimum opening state.

3. The multi-split air conditioner according to claim 2, characterized in that, The indoor unit controller is configured to terminate the increased opening control if the indoor unit ends its cooling cycle when the increased opening control is executed. When the indoor unit ends the cooling cycle or switches to another operating mode, the duration of the cooling cycle temperature control mode is reset to zero.

4. The multi-split air conditioner according to any one of claims 1 to 3, characterized in that, The indoor unit controller is configured with an increase in opening degree, a minimum opening degree, a second opening degree limit, and a third temperature limit; the initial value of the minimum opening degree is 0. The second opening limit is greater than the first opening limit; The increased opening control includes: Determine whether the minimum opening degree is 0; when it is 0, control the indoor unit's electronic expansion valve to close. After the indoor unit electronic expansion valve is closed, the opening degree of the indoor unit electronic expansion valve is increased at least once by the increased opening degree; after each increase in the increased opening degree, it is determined whether the opening degree of the indoor unit electronic expansion valve exceeds the second opening degree limit; if yes, the indoor unit electronic expansion valve is controlled to restore the superheat control; if no, it is determined whether the difference between the elbow temperature before the increase in the increased opening degree and the elbow temperature after the increase in the increased opening degree exceeds the third temperature limit, or whether the difference between the inlet temperature before the increase in the increased opening degree and the inlet temperature after the increase in the increased opening degree exceeds the third temperature limit, and if yes, it is determined that the indoor unit electronic expansion valve is open, and minimum opening degree storage control and superheat control are restored; if no, the indoor unit electronic expansion valve is controlled to continue to increase the increased opening degree.

5. The multi-split air conditioner according to claim 4, characterized in that, The minimum opening degree storage control includes: Determine whether the low pressure is lower than the first low pressure limit; If yes, then determine whether the current opening degree of the indoor unit electronic expansion valve exceeds the first opening degree limit. If yes, the first opening degree limit is stored to the minimum opening degree and the superheat control is restored. If no, the current opening degree of the indoor unit electronic expansion valve is stored to the minimum opening degree and the superheat control is restored. If not, then directly restore the superheat control.

6. The multi-split air conditioner according to claim 5, characterized in that, The increased opening control also includes: Determine whether the minimum opening degree is 0; if it is not 0, control the indoor unit's electronic expansion valve to open to the minimum opening degree; After the indoor unit electronic expansion valve is opened to the minimum opening degree, the opening degree of the indoor unit electronic expansion valve is increased at least once by the increased opening degree; after each increase in the increased opening degree, it is determined whether the opening degree of the indoor unit electronic expansion valve exceeds the second opening degree limit; if yes, the indoor unit electronic expansion valve is controlled to restore the superheat control; if no, it is determined whether the difference between the elbow temperature before the increase in the increased opening degree and the elbow temperature after the increase in the increased opening degree exceeds the third temperature limit or whether the difference between the inlet temperature before the increase in the increased opening degree and the inlet temperature after the increase in the increased opening degree exceeds the third temperature limit. If yes, it is determined that the indoor unit electronic expansion valve is open and the superheat control is restored; if no, the indoor unit electronic expansion valve is closed, and a confirmation judgment and control are performed.

7. The multi-split air conditioner according to claim 6, characterized in that, The indoor unit electronic expansion valve closure confirmation judgment and control includes: Determine whether the difference between the indoor temperature and the second temperature limit exceeds the inlet temperature, and whether the difference between the indoor temperature and the second temperature limit exceeds the elbow temperature; If yes, the indoor unit's electronic expansion valve resumes the superheat control; if no, the opening of the indoor unit's electronic expansion valve continues to increase.

8. The multi-split air conditioner according to claim 7, characterized in that, The indoor unit controller is configured with a second pressure limit, which is less than the first low pressure limit; the indoor unit controller is configured to determine whether the low pressure is lower than the second pressure limit when the indoor unit electronic expansion valve is in the minimum opening state; and when the low pressure is lower than the second pressure limit, control the opening of the indoor unit electronic expansion valve to increase to the second opening limit, and restore the superheat control.

9. The multi-split air conditioner according to claim 1, characterized in that, It also includes an outlet temperature sensor, which is installed at the outlet and connected to the indoor unit controller to detect the outlet temperature and transmit it to the indoor unit controller; the indoor unit controller is also configured with a superheat setting value; the superheat control is to perform intake superheat PI control by using the difference between the outlet temperature and the inlet temperature and the superheat setting value, which is used to control the opening of the indoor unit's electronic expansion valve.

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