WO2020192087A1

WO2020192087A1 - Multi-split air conditioner and control method therefor

Info

Publication number: WO2020192087A1
Application number: PCT/CN2019/110957
Authority: WO
Inventors: 任善军; 毛守博; 何建奇; 远义忠; 王洪伟
Original assignee: 青岛海尔空调电子有限公司; 海尔智家股份有限公司
Priority date: 2019-03-26
Filing date: 2019-10-14
Publication date: 2020-10-01
Also published as: CN110030757A

Abstract

A multi-split air conditioner, comprising a compressor (20), a four-way valve (3), a plurality of indoor units (1), a first outdoor heat exchanger (21) and a second outdoor heat exchanger (22) arranged in parallel, and a first outdoor-unit expansion valve (23) and a second outdoor-unit expansion valve (24) that match the first outdoor heat exchanger (21) and the second outdoor heat exchanger (22), respectively. The compressor (20), the four-way valve (3), the first outdoor heat exchanger (21), the first outdoor-unit expansion valve (23), and any indoor unit (1) constitute a first refrigerant circulation loop; the compressor (20), the four-way valve (3), the second outdoor heat exchanger (22), the second outdoor-unit expansion valve (24), and any indoor unit (1) constitute a second refrigerant circulation loop. The first outdoor-unit expansion valve (23) and the second outdoor-unit expansion valve (24) can close/open the first refrigerant circulation loop and the second refrigerant circulation loop, respectively.

Description

Multi-line air conditioner and its control method

Technical field

The invention belongs to the technical field of air conditioners, and specifically relates to a multi-line air conditioner and a control method thereof.

Background technique

Multi-line air conditioners usually match a larger number of indoor units and an outdoor unit (one or more) far less than the number of indoor units. According to the size and quantity of the room, some of the matching indoor units have a smaller horsepower setting. For example, in a multi-line system, there is 1 outdoor unit of 26HP, which can match 26 indoor units of 1HP. The ratio is 100%. According to the above configuration, the multi-line unit runs fully, and the multi-line system can operate normally and stably. However, because the outdoor unit is often designed with only one outdoor heat exchanger, if only one indoor unit is turned on, the outdoor heat exchanger corresponding to this indoor unit is larger at this time, which has the following defects: normal cooling/heating operation When the room temperature is relatively easy to reach the set temperature, the compressor may stop running. When the room temperature rises or falls, the unit is turned on again. Such repeated start and stop will consume more power and damage the unit. In addition, when the multi-line group is operating at a small load (especially low-temperature cooling operation), the outdoor heat exchanger is relatively large, which easily causes the multi-line group to fail to operate normally.

In order to avoid the problem that the outdoor heat exchanger is too large when the air conditioner is running at a small load, a prior application with the application number 201711373724.0 discloses an air conditioner system. The outdoor unit of the system includes at least two separate outdoor heat exchangers. Heat exchanger, but this system requires 3 four-way valves in parallel. By controlling the position of the four-way valve slide valve to change the flow direction of the refrigerant to realize the partition control of the outdoor heat exchanger, but in order to ensure the normal operation of the four-way valve, the four-way The valve nozzle needs to be connected to a capillary tube to ensure a certain pressure difference, so there will be a certain degree of refrigerant leakage. The refrigerant does not do work, but the compressor exhaust flows to the compressor to suck in. From the experimental data, this leakage will affect the capacity improvement, and There are three four-way valves in a unit, which will cause problems such as complicated pipelines, increased costs, and increased weld leakage failure rate.

Therefore, in view of the complicated piping of the entire air conditioner system caused by the structural design of the four-way valve in the previously disclosed air conditioner system, and the potential safety hazards, the present invention proposes a new multi-line air conditioner and its Control Method.

Summary of the invention

In order to solve the above-mentioned problems in the prior art, that is, in order to avoid frequent switching on and off of the compressor, while reducing the complexity of the pipeline of the multi-line air conditioner and eliminating the hidden safety problems of the existing air conditioner system, the present invention proposes a multi-line The air conditioner includes a plurality of indoor units and at least one outdoor unit. The outdoor unit includes at least a first outdoor heat exchanger and a second outdoor heat exchanger arranged in parallel, and a first outdoor heat exchanger matched with the first outdoor heat exchanger. The external machine expansion valve and the second external machine expansion valve matched with the second outdoor heat exchanger; the multi-line also includes a compressor and a four-way valve, the compressor, the four-way valve, the first An outdoor heat exchanger, the first outdoor unit expansion valve and any indoor unit form a first refrigerant circulation circuit; the compressor, the four-way valve, the second outdoor heat exchanger, the second The outdoor unit expansion valve and any indoor unit form a second refrigerant circulation circuit; the first outdoor unit expansion valve can close/open the first refrigerant circulation circuit, and the second outdoor unit expansion valve can close/open the The second refrigerant circulation circuit.

In the preferred embodiment of the above multi-line air conditioner, the outdoor unit further includes a first check valve arranged in parallel with the first outdoor unit expansion valve and a second check valve arranged in parallel with the second outdoor unit expansion valve. The first one-way valve only allows the refrigerant flowing out of the first heat exchanger to pass, and the second one-way valve only allows the refrigerant flowing out of the second heat exchanger to pass.

In the preferred embodiment of the above multi-line air conditioner, a partition is provided between the first outdoor heat exchanger and the second outdoor heat exchanger, and the partition separates the first outdoor heat exchanger and the The second outdoor heat exchanger is separated in different areas.

In a preferred embodiment of the above multi-line air conditioner, the outdoor unit further includes a first outdoor fan matched with the first outdoor heat exchanger and a second outdoor fan matched with the second outdoor heat exchanger The first outdoor fan is used to assist the first outdoor heat exchanger to dissipate cold/heat, and the second outdoor fan is used to assist the second outdoor heat exchanger to dissipate cold/heat.

In a preferred embodiment of the above-mentioned multi-line air conditioner, the outdoor unit includes more than three outdoor heat exchangers, wherein a partition is arranged between every two adjacent outdoor heat exchangers, and the partition is Used to separate the multiple outdoor heat exchangers in different areas; and/or, each outdoor heat exchanger is matched with a corresponding outdoor machine expansion valve; and/or, each outdoor heat exchanger is matched with The corresponding outdoor fan.

The present invention also provides a control method of a multi-line air conditioner. The multi-line air conditioner includes a plurality of indoor units and at least one outdoor unit. The outdoor unit includes: at least two outdoor heat exchangers arranged in parallel, and each An outdoor expansion valve matched with the outdoor heat exchanger and an outdoor fan matched with each outdoor heat exchanger, the expansion valve is used to control the flow of refrigerant passing through the corresponding indoor heat exchanger; The air conditioner control method includes the following steps: S110, determining whether the multi-line air conditioner satisfies the condition for individually controlling the amount of refrigerant entering each outdoor heat exchanger; S120, determining the waiting condition if the condition is satisfied The outdoor heat exchanger is closed and the outdoor expansion valve and the outdoor fan matched with the outdoor heat exchanger are closed.

In the preferred embodiment of the above-mentioned multi-line air conditioner control method, step S120 specifically includes: after determining the outdoor heat exchanger to be closed, gradually closing the opening of the outdoor expansion valve matching the outdoor heat exchanger to be closed. And the outdoor fan, and the opening of the outdoor expansion valve and the outdoor fan are completely closed within a set time.

In a preferred embodiment of the control method of the multi-line air conditioner, the control method of the multi-line air conditioner further includes: increasing the frequency of the compressor after the outdoor heat exchanger to be turned off is turned off.

In a preferred embodiment of the control method of the above multi-line air conditioner, the control method of the multi-line air conditioner further includes: after the outdoor heat exchanger to be closed is closed, detecting the performance of the outdoor heat exchanger to be closed Stop time; when the stop time exceeds the first preset time, the closed outdoor heat exchanger is opened, and the corresponding number of outdoor heat exchangers that have not been closed are closed.

In the preferred embodiment of the above-mentioned multi-line air conditioner control method, during the cooling operation of the multi-line air conditioner, in step S110, the conditions for individually controlling the amount of refrigerant entering each outdoor heat exchanger are as follows: Energy demand/total capacity of outdoor unit ≤ first preset value; outdoor ambient temperature ≤ first preset temperature; indoor ambient temperature-indoor coil temperature ≤ second preset temperature; duration of operation of the compressor at the lowest frequency ≥The second preset time; in the heating operation of the multi-connected air conditioner, in step S110, the conditions for individually controlling the amount of refrigerant entering each outdoor heat exchanger are as follows: total energy demand of the indoor unit/total outdoor unit Capacity ≤ second preset value; outdoor ambient temperature ≥ third preset temperature; indoor coil temperature-indoor ambient temperature ≤ fourth preset temperature; duration of operation of the compressor at the lowest frequency ≥ third preset time .

The present invention mainly changes the structure of the outdoor unit of the multi-line air conditioner. A plurality of outdoor heat exchangers are arranged in parallel in the outdoor unit, and then each outdoor heat exchanger is matched with a corresponding outdoor unit expansion valve, and the outdoor unit expansion valve is used Control the flow of refrigerant entering the corresponding outdoor heat exchanger, that is, after the outdoor unit expansion valve is completely closed, it is equivalent to disconnecting the outdoor heat exchanger from the refrigerant circulation system of the multi-line air conditioner. After the outdoor unit expansion valve is opened, the outdoor heat exchanger Will be connected to the refrigerant circulation system of the multi-line air conditioner. In this way, when multi-line partial load operation (a small number of indoor units are running), part of the outdoor heat exchanger can be closed (that is, to reduce the use area of the outdoor heat exchanger) by separately controlling the expansion valve of the external unit, which is achieved The purpose of matching the corresponding outdoor heat exchanger area according to the needs of the indoor unit, thus changing the traditional multi-line air conditioner in the partial load operation, the compressor runs at low frequency for a long time and constantly starts and stops, so that the compressor can maintain Stable operation in the mid-range, reducing the impact on the compressor life.

In addition, compared to the area control of the outdoor heat exchanger by controlling the position of the four-way valve slide valve to change the flow direction of the refrigerant as mentioned in the background art, the present invention does not need to design a complicated four-way valve structure. Under the premise of changing the structure of the four-way valve, use an outdoor expansion valve matched with the outdoor heat exchanger to control the amount of refrigerant entering the corresponding outdoor heat exchanger (that is, through the opening and closing of the outdoor expansion valve to make the matched outdoor exchange The heater is connected to or disconnected from the refrigerant cycle). In this way, the present invention only needs to match the corresponding outdoor unit expansion valve for each outdoor heat exchanger arranged in parallel in the outdoor unit, so that the same technical effect as the air conditioner system mentioned in the background art can be achieved, and also It avoids complicated piping design, greatly reduces the risk of refrigerant leakage, and further reduces production costs.

Description of the drawings

Figure 1 is a schematic structural diagram of a multi-connected air conditioner according to an embodiment of the present invention;

Fig. 2 is a main flow chart of the control method of the multi-connected air conditioner of the present invention.

detailed description

In order to make the embodiments, technical solutions and advantages of the present invention more obvious, the technical solutions of the present invention will be described clearly and completely in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of them. Examples. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

First, refer to FIG. 1, which is a schematic structural diagram of a multi-connected air conditioner according to an embodiment of the present invention. As shown in Fig. 1, the multi-line air conditioner of the present invention includes a plurality of indoor units 1 (four indoor units 1 are shown in Fig. 1) and at least one outdoor unit 2 (the dotted line in Fig. 1). The outdoor unit 2 includes at least a first outdoor heat exchanger 21 and a second outdoor heat exchanger 22 arranged in parallel, and a first outdoor unit expansion valve 23 matching the first outdoor heat exchanger 21 and a second outdoor heat exchanger 22 matching the second external machine expansion valve 24. The multi-line air conditioner of the present invention also includes a compressor 20 and a four-way valve 3. The compressor 20, the four-way valve 3, the first outdoor heat exchanger 21, the first outdoor unit expansion valve 23 and any indoor unit 1 constitute the first The refrigerant circulation circuit; the compressor 20, the four-way valve 3, the first outdoor heat exchanger 21, the first outdoor unit expansion valve 23 and any indoor unit 1 form a second refrigerant circulation circuit. The first external machine expansion valve 23 can close/open the first refrigerant circulation circuit, and the second external machine expansion valve 22 can close/open the second refrigerant circulation circuit. In other words, after the first outdoor unit expansion valve 23 is completely closed, it is equivalent to disconnecting the first outdoor heat exchanger 21 from the refrigerant circulation system of the multi-line air conditioner. After the first outdoor unit expansion valve 22 is opened, the first outdoor heat exchange The device 21 is connected to the refrigerant circulation system of the multi-line air conditioner. Similarly, after the second outdoor unit expansion valve 24 is completely closed, it is equivalent to disconnecting the second outdoor heat exchanger 22 from the refrigerant circulation system of the multi-line air conditioner. After the second outdoor unit expansion valve 24 is opened, the second outdoor heat exchange The device 22 is connected to the refrigerant circulation system of the multi-line air conditioner. In other words, the multi-line air conditioner of the present invention can individually control the flow of refrigerant in each outdoor heat exchanger. When one of the outdoor heat exchangers needs to be disconnected, only the external expansion valve of the corresponding outdoor heat exchanger Just close it.

Compared with the air conditioner system mentioned in the background art (hereinafter referred to as the existing solution), the present invention does not need to change the structure of the four-way valve, thereby avoiding the entire air conditioner refrigerant circulation caused by changing the structure of the four-way valve in the existing solution The complexity of the system pipeline. Those skilled in the art can understand that for the refrigerant circulation system, the more complicated the pipeline, the higher the risk of refrigerant leakage, and the present invention uses the one that matches the outdoor heat exchanger without changing the structure of the four-way valve. The external unit expansion valve controls the amount of refrigerant entering the corresponding outdoor heat exchanger (that is, through the opening and closing of the external unit expansion valve so that the matching outdoor heat exchanger is connected to or disconnected from the refrigerant cycle). In this way, the present invention only needs to match the corresponding outdoor expansion valve for each outdoor heat exchanger arranged in parallel in the outdoor unit, so that the same technical effect as the existing solution can be achieved, and complicated pipelines are also avoided. The design greatly reduces the risk of refrigerant leakage and further reduces production costs.

In addition, the outdoor expansion valve of the present invention may be an electronic expansion valve, which is used to adjust the amount of refrigerant passing through the outdoor heat exchanger. When the electronic expansion valve is completely closed, the amount of refrigerant passing through the corresponding outdoor heat exchanger is zero. The existing outdoor unit expansion valve is usually installed in the pipeline between the outdoor unit and the indoor unit to control the amount of refrigerant flowing from the indoor unit into the outdoor unit or the amount of refrigerant flowing out of the outdoor unit. According to the number of outdoor heat exchangers arranged in parallel in the outdoor unit, the present invention matches each outdoor heat exchanger with an electronic expansion valve, and each electronic expansion valve is used to control the matched outdoor heat exchanger.

Those skilled in the art can also divide the outdoor heat exchangers into more pieces according to actual needs, such as three, four, etc. According to the above-mentioned multi-line air conditioner structure design, each outdoor heat exchanger set in parallel in the outdoor unit can be exchanged It is controlled separately, that is, the refrigerant flow into each outdoor heat exchanger is separately controlled by controlling the outdoor expansion valve matched with the outdoor heat exchanger. When a small number of indoor units are running, it is not necessary to use all the outdoor heat exchangers. Heat exchange. At this time, a certain number of outdoor expansion valves can be closed, so that some outdoor heat exchangers can be connected to the refrigerant circulation system, which can effectively reduce the continuous low-frequency operation of the compressor for a long time and the continuous start and stop of the compressor. It can maintain stable operation in the mid-range, reducing the impact on the compressor life. For ease of understanding, this embodiment takes as an example the division of the outdoor heat exchanger into independent first outdoor heat exchanger 21 and second outdoor heat exchanger 22 for detailed description.

Since the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22 can work independently and do not affect each other, according to the structure design of the multi-line air conditioner of the present invention, when the multi-line part-load operation (such as a few indoor units) , Match the corresponding outdoor heat exchanger area according to the requirements of the indoor unit (the total area of the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22 can be used as the area of the outdoor heat exchanger, when the outdoor heat exchanger is required When the area is small, you can turn off one of the outdoor heat exchangers, which is equivalent to reducing the heat exchange area of the outdoor heat exchanger), which changes the traditional multi-line air conditioner during partial load operation, the compressor for a long time Low-frequency operation and continuous start and stop, so that the compressor can maintain stable operation in the mid-range, reducing the impact on the life of the compressor. The following is a further detailed description in conjunction with FIG. 1.

During the operation of the multi-line air conditioner, if the conditions for separately controlling the amount of refrigerant entering the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22 are met (see below for specific conditions), the first outdoor heat exchanger can be controlled separately. The external machine expansion valve 23 or the second external machine expansion valve 24 reduces the use area of the outdoor heat exchanger. Specifically, in the cooling operation of the multi-line air conditioner (the direction of the four-way valve 3 in Figure 1 is heating operation, and the direction of the four-way valve 3 needs to be changed during cooling operation), since the outdoor heat exchanger is on the high-pressure side, The outdoor unit expansion valve 23 and the second outdoor unit expansion valve 24 are respectively located at the front end of the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22 (that is, the position shown in FIG. 1), when the first outdoor unit expansion valve When 23 or the second outdoor expansion valve 24 is closed, the high temperature and high pressure refrigerant from the compressor 20 will enter the second outdoor heat exchanger 22 or the first outdoor heat exchanger 21, which will cause part of the refrigerant to accumulate in a certain outdoor heat exchanger. Heater situation. In this case, when the low pressure pressure sensor 4 detects that the system pressure is lower than the set value, the flow path of the first outdoor heat exchanger 21 or the second outdoor heat exchanger 22 can be opened (open the first outdoor heat exchanger to expand Valve 23 or the second external machine expansion valve 24) to ensure that the refrigerant circulates in the system. When the low pressure pressure sensor 4 detects that the system pressure rises to the set value, the first external machine expansion valve 23 or the second external machine expansion valve is closed twenty four.

In the heating operation of the multi-line air conditioner (the direction of the four-way valve 3 in FIG. 1 is the heating operation), since the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22 are on the low pressure side at this time, the first An outdoor machine expansion valve 23 and a second outdoor machine expansion valve 24 are located at the front end of the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22 (ie the position shown in FIG. 1), so there is no refrigerant accumulation in In the case of a certain outdoor heat exchanger, in this case, as long as the requirements of the indoor unit can be met, the first outdoor unit expansion valve 23 or the second outdoor unit expansion valve 24 can be normally closed.

As a possible implementation, the first outdoor machine expansion valve 23 and the second outdoor machine expansion valve 24 can also be arranged at the rear end of the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22 (according to Figure 1 The orientation is above the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22).

1, the outdoor unit 2 of the present invention further includes a first check valve 25 arranged in parallel with the first outdoor unit expansion valve 23 and a second check valve 26 arranged in parallel with the second outdoor unit expansion valve 24. The first check valve 25 only allows the refrigerant flowing from the first heat exchanger 21 to pass, and the second check valve 26 only allows the refrigerant flowing from the second heat exchanger 22 to pass. The outdoor unit 2 also includes a first outdoor fan 27 matched with the first outdoor heat exchanger 21 and a second outdoor fan 28 matched with the second outdoor heat exchanger 22; the first outdoor fan 27 is used to assist the first outdoor heat exchanger. The outdoor heat exchanger 21 radiates cold/heat, and the second outdoor fan 28 is used to assist the second outdoor heat exchanger 22 to radiate cold/heat. When the first outdoor machine expansion valve 23 or the second outdoor machine expansion valve 24 is closed, the corresponding first outdoor machine fan 27 and the second outdoor machine fan 28 are turned off at the same time. It should be noted that during multi-line refrigeration operation, the refrigerant will still flow through the one-way valve after closing the outdoor expansion valve. However, after the outdoor expansion valve is closed, the corresponding outdoor fan will also be turned off. Play a certain role to disconnect part of the outdoor heat exchanger. Obviously, the one-way valve here is not necessary, and those skilled in the art can choose whether to match the one-way valve connected in parallel with the external machine expansion valve according to actual needs.

In a specific embodiment, a partition 29 is provided between the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22, and the partition 29 separates the first outdoor heat exchanger 21 and the second outdoor heat exchanger. 22 separated in different areas. Since the partition 29 divides the indoor unit into two different areas, the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22 respectively located in the two areas can not affect each other. When the outdoor heat exchanger needs to be fully utilized, the first outdoor fan 27 and the second outdoor fan 28 operate at the same time, and the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22 are turned on at the same time. The air conditioner (without the bottom partition) has the same heat exchange effect; when the outdoor unit heat exchanger does not need to be used all, for example, the first outdoor unit fan 27 can be stopped, and the flow path of the first outdoor heat exchanger 21 can be closed at the same time. The second outdoor fan 28 is operated while the second outdoor heat exchanger 22 circulates.

It should be noted again that although the outdoor heat exchanger mentioned above is divided into the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22, those skilled in the art can divide the outdoor heat exchanger into more according to actual needs. Then, a partition can be set between two adjacent outdoor heat exchangers. The partition divides the outdoor unit into multiple different areas, each area has an outdoor heat exchanger, and then each The outdoor heat exchanger matches the corresponding outdoor machine expansion valve and outdoor machine fan. In this way, different numbers of outdoor heat exchangers can be turned off according to the needs of the indoor unit, so as to more accurately match the demand of the indoor unit with the area of the outdoor heat exchanger in use, so that the compressor can be kept in the mid-range. Stable operation reduces the impact on the life of the compressor. In addition, it should be noted that because the partition 29 is provided in the outdoor unit, different outdoor heat exchangers in the outdoor unit can be separated in different areas, so that the outdoor fan matching the outdoor heat exchanger is also divided. In different areas. In this way, the outdoor heat exchanger and outdoor fan in each area can work independently without affecting each other. Compared with the situation without partitions, it effectively avoids the easy operation of the outdoor fan matching the outdoor heat exchanger. Affect the outdoor heat exchanger that does not match it.

In a specific embodiment, the main components of the multi-line air conditioner of the present invention further include a high-pressure pressure sensor 5, an oil separator 6, a one-way valve 7, a gas-liquid separator 8, etc., which will not be described again in detail.

The present invention also provides a control method for a multi-line air conditioner. The multi-line air conditioner includes a plurality of indoor units and at least one outdoor unit. The outdoor unit includes at least two outdoor heat exchangers arranged in parallel and exchanges heat with each outdoor unit. An outdoor expansion valve matched with an outdoor heat exchanger and an outdoor fan matched with each outdoor heat exchanger. The expansion valve is used to control the flow of refrigerant through the corresponding indoor heat exchanger (see the above multi-line air conditioner for details). Referring to Figure 2, Figure 2 is a main flow chart of the control method of the multi-connected air conditioner of the present invention. As shown in Figure 2, the control method of the multi-connected air conditioner of the present invention includes the following steps: S110, judging whether the multi-connected air conditioner satisfies the conditions for individually controlling the amount of refrigerant entering each outdoor heat exchanger; S120, when the Under conditions, determine the outdoor heat exchanger to be closed and close the outdoor expansion valve and outdoor fan matching the outdoor heat exchanger.

For ease of understanding, the following takes the multi-connected air conditioner shown in FIG. 1 as an example for detailed description. In step S120, if the conditions for separately controlling the amount of refrigerant entering the first outdoor heat exchanger 21 and the second outdoor heat exchanger 22 are met, it is assumed that the first outdoor heat exchanger 21 is to be shut down, and then the first outdoor heat exchanger 21 can be shut down gradually. The opening of the first outdoor machine expansion valve 23 and the first outdoor machine fan 27 expand the first outdoor machine within a set time, such as 2 minutes (or other reasonable time, such as 1 minute, 3 minutes, etc.) The valve 23 and the first outdoor fan 27 are completely closed.

At this time, since the area of the outdoor heat exchanger becomes smaller, in order to achieve the indoor target coil temperature, the operating frequency of the compressor 20 needs to be increased. Specifically, the frequency of the compressor 20 can be up-frequency controlled according to the detected system pressure and the temperature of the indoor coil, or it can be adjusted by adjusting the first outdoor expansion valve 23 of the first outdoor heat exchanger 21 that has just been closed and the corresponding The first outdoor fan 27 performs frequency-up control on the compressor 20 to ensure that the compressor 20 operates in the frequency band corresponding to the best energy efficiency. Regarding how to increase the frequency of the compressor 20, those skilled in the art can flexibly choose different methods, as long as the compressor 20 is operated in the frequency band with the best energy efficiency.

As an example, still taking the closing of the first outdoor heat exchanger 21 in FIG. 1 as an example, after the first outdoor heat exchanger 21 is closed, the stop time of the first outdoor heat exchanger 21 is detected. When the stop time exceeds the first preset time, the first outdoor heat exchanger 21 is opened, and the second outdoor heat exchanger 22 is closed (that is, the second outdoor expansion valve 24 and the second outdoor fan 26 are gradually closed). In this way, it is possible to avoid the difference in the service life between different outdoor heat exchangers due to the difference in operating time, so that the operating time of different outdoor heat exchangers is close. The aforementioned first preset time can be flexibly set by those skilled in the art, and the first preset time is not limited here.

When the multi-line air conditioner is in refrigeration operation, in step S110, the conditions for individually controlling the amount of refrigerant entering each outdoor heat exchanger are as follows: (1) Total energy demand of indoor unit/total capacity of outdoor unit ≤ preset value; 2) Outdoor ambient temperature ≤ first preset temperature; (3) Indoor ambient temperature-indoor coil temperature ≤ second preset temperature; (4) Duration of compressor operation at the lowest frequency ≥ second preset time.

It should be noted that the first preset value in the above condition (1) may be 50%, that is, the total energy of the indoor unit must be half of the total capacity of the outdoor unit at this time. Those skilled in the art can choose other reasonable first preset values, such as 60%, 40%, and so on. The first preset temperature in the above condition (2) may be 20°C, and those skilled in the art can choose other reasonable first preset temperatures, such as 25°C. The second preset temperature in the above condition (3) may be 2°C, and those skilled in the art can choose other reasonable second preset temperatures, such as 3°C. The second preset time in the above condition (4) may be 10 minutes, and those skilled in the art can choose other reasonable second preset time, such as 9 minutes. Those skilled in the art can understand that when the compressor runs at the lowest frequency, it indicates that the area of the outdoor heat exchanger is too large. After the above conditions are met, the different outdoor heat exchangers of the outdoor unit can be individually controlled.

As an example, when the multi-line air conditioner does not meet any of the above conditions, it exits the separate control of different outdoor heat exchangers of the outdoor unit. At this time, all outdoor heat exchangers are simultaneously controlled.

In the heating operation of the multi-line air conditioner, in step S110, the conditions for individually controlling the amount of refrigerant entering each outdoor heat exchanger are as follows: (1) Total energy demand of indoor units/total capacity of outdoor units ≤ second preset Value; (2) Outdoor ambient temperature ≥ third preset temperature; (3) Indoor coil temperature-indoor ambient temperature ≤ fourth preset temperature; (4) Duration of compressor operation at the lowest frequency ≥ third preset time.

It should be noted that the second preset value in the above condition (1) may be 50%, that is, the total energy of the indoor unit must be half of the total capacity of the outdoor unit at this time. Those skilled in the art can choose other reasonable second preset values, such as 60%, 40%, etc. The third preset temperature in the above condition (2) may be 20°C, and those skilled in the art can choose other reasonable third preset temperatures, such as 25°C. The fourth preset temperature in the above condition (3) may be 2°C, and those skilled in the art can choose other reasonable fourth preset temperatures, such as 3°C. The third preset time in the above condition (4) may be 10 minutes, and those skilled in the art can choose other reasonable third preset time, such as 9 minutes. Those skilled in the art can understand that when the compressor runs at the lowest frequency, it indicates that the area of the outdoor heat exchanger is too large. After all the above conditions are met, the different outdoor heat exchangers of the outdoor unit can be individually controlled.

So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the drawings. However, those skilled in the art will readily understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

A multi-line air conditioner, comprising a plurality of indoor units and at least one outdoor unit, characterized in that the outdoor unit includes at least a first outdoor heat exchanger and a second outdoor heat exchanger arranged in parallel, and is connected to the first outdoor heat exchanger. A first outdoor unit expansion valve matched with the outdoor heat exchanger and a second outdoor unit expansion valve matched with the second outdoor heat exchanger;

The multi-line air conditioner also includes a compressor and a four-way valve. The compressor, the four-way valve, the first outdoor heat exchanger, the first outdoor unit expansion valve and any one indoor unit form a first Refrigerant circulation circuit; the compressor, the four-way valve, the second outdoor heat exchanger, the second outdoor unit expansion valve and any indoor unit form a second refrigerant circulation circuit;

The first external machine expansion valve can close/open the first refrigerant circulation circuit, and the second external machine expansion valve can close/open the second refrigerant circulation circuit.
The multi-line air conditioner according to claim 1, wherein the outdoor unit further comprises a first one-way valve arranged in parallel with the first outdoor unit expansion valve and a first check valve arranged in parallel with the second outdoor unit expansion valve The second one-way valve;

The first one-way valve only allows the refrigerant flowing out of the first heat exchanger to pass through, and the second one-way valve only allows the refrigerant flowing out of the second heat exchanger to pass through.
The multi-line air conditioner according to claim 1, wherein a partition is provided between the first outdoor heat exchanger and the second outdoor heat exchanger,

The partition plate separates the first outdoor heat exchanger and the second outdoor heat exchanger in different areas.
The multi-line air conditioner according to any one of claims 1 to 3, wherein the outdoor unit further comprises a first outdoor fan matched with the first outdoor heat exchanger and a fan with the second outdoor unit. The second outdoor fan matching the heat exchanger;

The first outdoor fan is used to assist the first outdoor heat exchanger to radiate cold/heat, and the second outdoor fan is used to assist the second outdoor heat exchanger to radiate cold/heat.
The multi-line air conditioner according to claim 1, wherein the outdoor unit comprises more than three outdoor heat exchangers, wherein:

A partition is provided between every two adjacent outdoor heat exchangers, and the partition is used to separate the multiple outdoor heat exchangers in different areas; and/or,

Each outdoor heat exchanger is matched with a corresponding outdoor expansion valve; and/or,

Each outdoor heat exchanger is matched with a corresponding outdoor fan.
A control method for a multi-line air conditioner, the multi-line air conditioner includes a plurality of indoor units and at least one outdoor unit, wherein the outdoor unit includes: at least two outdoor heat exchangers arranged in parallel, and each An outdoor expansion valve matched with the outdoor heat exchanger and an outdoor fan matched with each outdoor heat exchanger, the expansion valve being used to control the flow of refrigerant passing through the corresponding indoor heat exchanger;

The control method of the multi-line air conditioner includes the following steps:

S110: Determine whether the multi-line air conditioner satisfies a condition for individually controlling the amount of refrigerant entering each outdoor heat exchanger;

S120. When the conditions are met, determine the outdoor heat exchanger to be closed, and close the outdoor expansion valve and the outdoor fan matching the outdoor heat exchanger.
The control method of a multi-connected air conditioner according to claim 6, wherein step S120 specifically includes:

After determining the outdoor heat exchanger to be closed, gradually close the opening degree of the outdoor expansion valve and the outdoor fan that match the outdoor heat exchanger to be closed, and make the outdoor expansion valve within a set time The opening degree and the outside machine fan are completely shut off.
The control method of the multi-line air conditioner according to claim 7, wherein the control method of the multi-line air conditioner further comprises:

After the outdoor heat exchanger to be shut down is shut down, the frequency of the compressor is increased.
The control method of the multi-connected air conditioner according to claim 8, wherein the control method of the multi-connected air conditioner further comprises:

After the outdoor heat exchanger to be closed is closed, detecting the stop time of the outdoor heat exchanger to be closed;

When the stop time exceeds the first preset time, the closed outdoor heat exchanger is opened, and the corresponding number of outdoor heat exchangers that have not been closed are closed.
The control method of a multi-connected air conditioner according to any one of claims 6 to 9, wherein:

When the multi-line air conditioner is in refrigeration operation, in step S110, the conditions for individually controlling the amount of refrigerant entering each outdoor heat exchanger are as follows:

The total energy demand of the indoor unit/total capacity of the outdoor unit ≤ the first preset value;

Outdoor ambient temperature ≤ first preset temperature;

Indoor ambient temperature-indoor coil temperature ≤ second preset temperature;

The duration of the compressor running at the lowest frequency≥the second preset time;

In the heating operation of the multi-line air conditioner, in step S110, the conditions for individually controlling the amount of refrigerant entering each outdoor heat exchanger are as follows:

Total energy demand of indoor unit/total capacity of outdoor unit ≤ second preset value;

Outdoor ambient temperature ≥ the third preset temperature;

Indoor coil temperature-indoor ambient temperature ≤ the fourth preset temperature;

The duration of the compressor running at the lowest frequency≥the third preset time.