Air conditioner

Abstract

The embodiment of the invention belongs to the technical field of household electrical appliances, and provides an air conditioner which comprises an outdoor unit, an indoor unit and an outdoor unit, the indoor unit comprises a first indoor heat exchanger and a second indoor heat exchanger; when the first indoor heat exchanger and the second indoor heat exchanger both operate as evaporators and the two outdoor heat exchangers both operate as condensers, the controller controls the first indoor heat exchanger and the second indoor heat exchanger to operate; if the operation frequency H of the compressor is equal to the minimum frequency Hmin of the compressor, the rotating speed N of the outdoor fan is equal to the minimum rotating speed Nmin of the outdoor fan, and the exhaust pressure Pd of the compressor is smaller than the preset exhaust pressure Pdmin, one of the two outdoor heat exchangers is switched to be operated by an evaporator; the heat exchange area of the outdoor heat exchanger is reduced, the output capacity of the outdoor unit is reduced, the situation of lagging judgment of small-load working conditions is avoided, state switching lagging of the outdoor heat exchanger is avoided, shutdown of a compressor is avoided, and the reliability of the unit is protected.

Description

Technical Field

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

[0002] An air conditioner generally consists of an indoor unit and an outdoor unit. The indoor unit typically has an indoor heat exchanger, while the outdoor unit typically has an outdoor heat exchanger, a compressor, and an outdoor fan to achieve cooling or heating.

[0003] Air conditioners may experience low-load operation during operation. Low-load operation typically occurs in scenarios such as: a small number of indoor units are turned on by the user; a small difference between the outdoor ambient temperature and the set target temperature, and a small difference between the indoor ambient temperature and the set target temperature; extreme conditions: for example, cooling when the outdoor ambient temperature is -5℃ and the indoor ambient temperature is 20℃, and heating when the outdoor ambient temperature is 20℃ and the indoor ambient temperature is 32℃.

[0004] However, the judgment of low-load operating conditions in related technologies is relatively lagging, resulting in frequent compressor shutdowns, large fluctuations in indoor ambient temperature, and excessively low or high indoor air outlet temperatures, affecting user comfort. Therefore, this application proposes an air conditioner. Summary of the Invention

[0005] This application provides an air conditioner that can solve the technical problems of relatively delayed judgment of low-load operating conditions, frequent compressor shutdowns, large fluctuations in indoor ambient temperature, and excessively low or high indoor air outlet temperature.

[0006] In a first aspect, embodiments of this application provide an air conditioner, comprising:

[0007] The outdoor unit includes a compressor and two outdoor heat exchangers;

[0008] An indoor unit having at least one and including a first indoor heat exchanger and a second indoor heat exchanger;

[0009] A first pressure detection device is used to detect the discharge pressure of the compressor;

[0010] A controller, connected to the first pressure detection device, is configured to:

[0011] When both the first and second indoor heat exchangers are operating as evaporators, and both outdoor heat exchangers are operating as condensers, if the operating frequency H of the compressor is equal to the minimum frequency Hmin of the compressor, the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, and the discharge pressure Pd of the compressor is less than the preset discharge pressure Pdmin, then one of the two outdoor heat exchangers will be switched to evaporator operation.

[0012] When operating in basic cooling mode, once the compressor's operating frequency H equals the compressor's minimum frequency Hmin and the outdoor fan's speed N equals the outdoor fan's minimum speed Nmin, the compressor frequency and outdoor fan speed cannot be further reduced. If the outdoor unit's output capacity is still relatively high, the compressor's discharge pressure will first decrease to the minimum allowable value compared to the compressor's suction pressure. Therefore, the compressor's discharge pressure Pd is compared with the preset discharge pressure Pdmin. When the compressor's discharge pressure Pd is less than the preset discharge pressure Pdmin, one of the outdoor heat exchangers is switched to an evaporator to reduce the heat exchange area of ​​the outdoor heat exchanger, thereby reducing the outdoor unit's output capacity. This avoids delayed judgment of low-load conditions, delays in the outdoor heat exchanger's state switching, and prevents the compressor's discharge pressure Pd from further decreasing below the normal range, thus preventing compressor shutdown and protecting the unit's reliability.

[0013] According to one embodiment of this application, the controller is configured as follows:

[0014] When both the first and second indoor heat exchangers operate as evaporators, and both outdoor heat exchangers operate as condensers, if the compressor's operating frequency H is equal to the compressor's minimum frequency Hmin, the outdoor fan's speed N is equal to the outdoor fan's minimum speed Nmin, the compressor's discharge pressure Pd is greater than or equal to the preset discharge pressure Pdmin, and the difference between the indoor unit's return air temperature Ti and the set target temperature Ts is less than the first set value, then one of the two outdoor heat exchangers will be switched to evaporator operation.

[0015] This configuration reduces the heat exchange area of ​​the outdoor heat exchanger, lowers the output capacity of the outdoor unit, and prevents the compressor from frequently starting and stopping due to the small difference between the return air temperature of the indoor unit and the set target temperature, thus extending the compressor's lifespan.

[0016] According to one embodiment of this application, the indoor unit has an indoor air outlet, and the first indoor heat exchanger is located on the side of the second indoor heat exchanger near the indoor air outlet;

[0017] The controller is configured to:

[0018] When both the first and second indoor heat exchangers operate as evaporators, and the two outdoor heat exchangers operate as evaporators and condensers respectively, if the increase in compressor frequency required by the air conditioner ΔH is less than or equal to a second preset value, and the outlet air temperature To of the indoor unit is less than a third preset value, then the first indoor heat exchanger is switched to condenser operation. This setting reduces the heat exchange area of ​​the indoor heat exchangers, decreases the output of cooling capacity, and avoids discomfort caused by excessively low indoor outlet air temperature.

[0019] According to one embodiment of this application, the controller is configured as follows:

[0020] When both the first and second indoor heat exchangers operate as evaporators, and the two outdoor heat exchangers operate as evaporators and condensers respectively, if the increase in compressor frequency required by the air conditioner ΔH is less than or equal to a second preset value, the outlet air temperature To of the indoor unit is greater than or equal to a third preset value, and the difference between the return air temperature Ti of the indoor unit and the set target temperature Ts is less than a fourth preset value, then the first indoor heat exchanger is switched to condenser operation.

[0021] This configuration increases the heat exchange area of ​​the indoor heat exchanger, reduces the output of cooling capacity, and avoids frequent compressor start-stop cycles caused by a small difference between the indoor unit's return air temperature Ti and the set target temperature Ts, thus extending the compressor's lifespan.

[0022] According to one embodiment of this application, the indoor unit is provided with an indoor air outlet, and the first indoor heat exchanger is located on the side of the second indoor heat exchanger closer to the indoor air outlet;

[0023] The controller is configured to:

[0024] When the first indoor heat exchanger operates as a condenser, the second indoor heat exchanger operates as an evaporator, and both outdoor heat exchangers operate as condensers, if the compressor's operating frequency H is equal to the compressor's minimum frequency Hmin, the outdoor fan's speed N is equal to the outdoor fan's minimum speed Nmin, and the compressor's discharge pressure Pd is less than the preset discharge pressure Pdmin, then one of the two outdoor heat exchangers will be switched to evaporator operation.

[0025] When operating in basic reheat dehumidification mode, once the compressor's operating frequency equals the compressor's minimum frequency Hmin and the outdoor fan's speed equals the outdoor fan's minimum speed Nmin, the compressor frequency and outdoor fan speed cannot be further reduced. If the outdoor unit's output capacity is still relatively high, the compressor's discharge pressure will first decrease to the minimum allowable value compared to the compressor's suction pressure. Therefore, the compressor's discharge pressure Pd is compared with the preset discharge pressure Pdmin. When the compressor's discharge pressure Pd is less than the preset discharge pressure Pdmin, one of the outdoor heat exchangers is switched to an evaporator to reduce the heat exchange area of ​​the outdoor heat exchanger, thereby reducing the outdoor unit's output capacity. This avoids delayed judgment of low-load conditions, delays in the outdoor heat exchanger's state switching, and prevents the compressor's discharge pressure Pd from further decreasing below the normal range, thus preventing compressor shutdown and protecting the unit's reliability.

[0026] According to one embodiment of this application, the controller is configured as follows:

[0027] When the first indoor heat exchanger operates as a condenser, the second indoor heat exchanger operates as an evaporator, and both outdoor heat exchangers operate as condensers, if the compressor's operating frequency H is equal to the compressor's minimum frequency Hmin, the outdoor fan's speed N is equal to the outdoor fan's minimum speed Nmin, the compressor's discharge pressure Pd is greater than or equal to the preset discharge pressure Pdmin, and the difference between the indoor unit's return air temperature Ti and the set target temperature Ts is less than the tenth set value, then one of the two outdoor heat exchangers will be switched to evaporator operation.

[0028] This configuration reduces the heat exchange area of ​​the outdoor heat exchanger, lowers the output capacity of the outdoor unit, and prevents the compressor from frequently starting and stopping due to the small difference between the return air temperature of the indoor unit and the set target temperature, thus extending the compressor's lifespan.

[0029] According to one embodiment of this application, it also includes:

[0030] The second pressure detection device is used to detect the suction pressure of the compressor and is connected to the controller;

[0031] The controller is configured to:

[0032] When both the first and second indoor heat exchangers are operating as condensers, and both outdoor heat exchangers are operating as evaporators, if the operating frequency H of the compressor is equal to the minimum frequency Hmin of the compressor, the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, and the suction pressure Ps of the compressor is greater than the preset suction pressure Psmax, then one of the two outdoor heat exchangers will be switched to condenser operation.

[0033] When operating in basic heating mode, once the compressor's operating frequency equals the compressor's minimum frequency Hmin and the outdoor fan's speed equals the outdoor fan's minimum speed Nmin, the compressor frequency and outdoor fan speed cannot be further reduced. If the outdoor unit's output capacity is still relatively high, compared to the compressor's discharge pressure, the compressor's suction pressure will first rise to the maximum allowable suction pressure. Therefore, when the compressor's suction pressure Ps is set to be greater than the preset suction pressure Psmax, one of the outdoor heat exchangers is controlled to switch to evaporator operation, reducing the heat exchange area of ​​the outdoor heat exchanger, reducing the outdoor unit's output capacity, avoiding delayed judgment of low-load conditions, avoiding delayed state switching of the outdoor heat exchanger, preventing the compressor's suction pressure Ps from further increasing to exceed the normal range of compressor suction pressure, avoiding compressor shutdown, and protecting the unit's reliability.

[0034] According to one embodiment of this application, the controller is configured as follows:

[0035] When both the first and second indoor heat exchangers operate as condensers, and both outdoor heat exchangers operate as evaporators, if the compressor's operating frequency H is equal to the compressor's minimum frequency Hmin, the outdoor fan's speed N is equal to the outdoor fan's minimum speed Nmin, the compressor's suction pressure Ps is less than or equal to the preset discharge pressure Psmax, and the difference between the set target temperature Ts and the indoor unit's return air temperature Ti is less than a sixth set value, then one of the two outdoor heat exchangers will be switched to condenser operation.

[0036] This configuration reduces the heat exchange area of ​​the outdoor heat exchanger, lowers the output capacity of the outdoor unit, and avoids frequent compressor start-stop cycles caused by a small difference between the set target temperature and the indoor unit's return air temperature, thus extending the compressor's lifespan.

[0037] According to one embodiment of this application, the controller is configured as follows:

[0038] When both the first and second indoor heat exchangers operate as condensers, and the two outdoor heat exchangers operate as evaporators and condensers respectively, if the increase in compressor frequency required by the air conditioner ΔH is less than or equal to the seventh preset value and the outlet air temperature To of the indoor unit is greater than the eighth preset value, then the first indoor heat exchanger is switched to evaporator operation. This setting can reduce the heat exchange area of ​​the indoor heat exchangers, reduce heat output, and avoid discomfort caused by excessively high indoor outlet air temperature.

[0039] And / or, when both the first and second indoor heat exchangers operate as condensers, and the two outdoor heat exchangers operate as evaporators and condensers respectively, if the increase in compressor frequency required by the air conditioner ΔH is less than or equal to a seventh preset value, the outlet air temperature To of the indoor unit is less than or equal to an eighth preset value, and the difference between the set target temperature Ts and the return air temperature Ti of the indoor unit is less than a ninth preset value, then the first indoor heat exchanger switches to evaporator operation. This setting can increase the heat exchange area of ​​the indoor heat exchanger, reduce heat output, avoid frequent compressor start-stop due to the small difference between the set target temperature Ts and the return air temperature Ti of the indoor unit, and improve the service life of the compressor.

[0040] Secondly, embodiments of this application provide an air conditioner, including:

[0041] The outdoor unit includes a compressor and two outdoor heat exchangers;

[0042] An indoor unit having at least one and including a first indoor heat exchanger and a second indoor heat exchanger;

[0043] The second pressure detection device is used to detect the suction pressure of the compressor;

[0044] A controller, connected to the second pressure detection device, is configured to:

[0045] When both the first and second indoor heat exchangers are operating as condensers, and both outdoor heat exchangers are operating as evaporators, if the operating frequency H of the compressor is equal to the minimum frequency Hmin of the compressor, the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, and the suction pressure Ps of the compressor is greater than the preset suction pressure Psmax, then one of the two outdoor heat exchangers will be switched to condenser operation.

[0046] When operating in basic heating mode, if the outdoor unit's output capacity is still relatively high, the compressor's suction pressure will rise to the maximum allowable suction pressure before the compressor's discharge pressure. Therefore, when the compressor's suction pressure Ps is set to be greater than the preset suction pressure Psmax, one of the outdoor heat exchangers will be switched to evaporator operation to reduce the heat exchange area of ​​the outdoor heat exchanger, reduce the outdoor unit's output capacity, avoid delayed judgment of low-load conditions, avoid delayed state switching of the outdoor heat exchanger, prevent the compressor's suction pressure Ps from further increasing and exceeding the normal range of the compressor's suction pressure, prevent the compressor from shutting down, and protect the unit's reliability. Attached Figure Description

[0047] To more clearly illustrate the implementation methods in the embodiments of this application or related technologies, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0048] Figure 1 This is a connection diagram of an air conditioner according to an embodiment of this application;

[0049] Figure 2 This is a connection diagram of the outdoor unit according to an embodiment of this application;

[0050] Figure 3 This is a connection diagram of an indoor unit according to an embodiment of this application;

[0051] Figure 4 This is a refrigerant flow diagram of an air conditioner operating in the first mode according to an embodiment of this application;

[0052] Figure 5This is a diagram showing the refrigerant flow direction when the air conditioner is operating in the second mode according to an embodiment of this application;

[0053] Figure 6 This is a diagram showing the refrigerant flow direction when the air conditioner is operating in the third mode according to an embodiment of this application;

[0054] Figure 7 This is a diagram showing the refrigerant flow direction of an air conditioner in its fifth operating mode according to an embodiment of this application.

[0055] Figure 8 This is a diagram showing the refrigerant flow direction when the air conditioner is operating in the fourth mode according to an embodiment of this application;

[0056] Figure 9 This is a refrigerant flow diagram of an air conditioner operating in a low-load cooling mode according to an embodiment of this application;

[0057] Figure 10 This is a refrigerant flow diagram of an air conditioner operating in a low-load second mode according to an embodiment of this application;

[0058] Figure 11 This is a refrigerant flow diagram of the first mode of low-load heating operation of an air conditioner according to an embodiment of this application;

[0059] Figure 12 This is a refrigerant flow diagram of the second mode of low-load heating operation of an air conditioner according to an embodiment of this application;

[0060] Figure 13 This is a refrigerant flow diagram of an air conditioner operating in reheat dehumidification low-load mode according to an embodiment of this application;

[0061] Figure 14 This is a control flowchart of an embodiment of this application;

[0062] Figure 15 This is another control flowchart of an embodiment of this application;

[0063] Figure 16 This is another control flowchart of an embodiment of this application.

[0064] Explanation of reference numerals in the attached figures:

[0065] 1-Outdoor unit; 11-Compressor; 121-First outdoor heat exchanger; 122-Second outdoor heat exchanger; 131-First throttling element; 132-Second throttling element; 141-First reversing device; 142-Second reversing device; 143-Third reversing device; 144-Fourth reversing device; 15-Gas-liquid separator; 161-First shut-off valve; 162-Second shut-off valve; 163-Third shut-off valve; 171-First outdoor fan; 172-Second outdoor fan; 2-Indoor unit; 211-First indoor heat exchanger; 212-Second indoor heat exchanger; 221-Third throttling element; 222-Fourth throttling element; 231-First switching device; 232-Second switching device; 233-Third switching device; 31-First piping; 32-Second piping; 33-Third piping. Detailed Implementation

[0066] 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.

[0067] Air conditioners may experience low-load conditions during operation. These low-load conditions typically occur in scenarios such as: a small number of indoor units being turned on; a small difference between the outdoor ambient temperature and the set target temperature; and extreme conditions, such as cooling at an outdoor ambient temperature of -5°C and an indoor ambient temperature of 20°C, or heating at an outdoor ambient temperature of 20°C and an indoor ambient temperature of 32°C. Under these low-load conditions, the compressor will reduce its frequency and the outdoor fan will reduce its speed to decrease the outdoor unit's output capacity. However, the compressor frequency and outdoor fan speed cannot be reduced indefinitely, ensuring that the outdoor unit's output capacity remains relatively high. However, current technologies are relatively slow to detect low-load conditions and cannot adjust accordingly in a timely manner, leading to frequent compressor shutdowns, large fluctuations in indoor ambient temperature, and excessively low or high indoor air outlet temperatures, thus affecting user comfort.

[0068] To address the aforementioned technical problems, this application proposes an air conditioner comprising an outdoor unit, an indoor unit, a first pressure detection device, and a controller. The outdoor unit includes a compressor and two outdoor heat exchangers; the indoor unit has at least one and includes a first indoor heat exchanger and a second indoor heat exchanger; the first pressure detection device is used to detect the compressor's discharge pressure; the controller is connected to the first pressure detection device and is configured to: when both the first and second indoor heat exchangers operate as evaporators, and both outdoor heat exchangers operate as condensers, if the compressor's operating frequency H equals the compressor's minimum frequency Hmin, the outdoor fan's speed N equals the outdoor fan's minimum speed Nmin, and the compressor's discharge pressure Pd is less than a preset discharge pressure Pdmin, then one of the two outdoor heat exchangers is switched to evaporator operation. When operating in basic cooling mode, once the compressor's operating frequency H equals the compressor's minimum frequency Hmin and the outdoor fan's speed N equals the outdoor fan's minimum speed Nmin, the compressor frequency and outdoor fan speed cannot be further reduced. If the outdoor unit's output capacity is still relatively high, the compressor's discharge pressure will first decrease to the minimum allowable value compared to the compressor's suction pressure. Therefore, the compressor's discharge pressure Pd is compared with the preset discharge pressure Pdmin. When the compressor's discharge pressure Pd is less than the preset discharge pressure Pdmin, one of the outdoor heat exchangers is switched to an evaporator to reduce the heat exchange area of ​​the outdoor heat exchanger, thereby reducing the outdoor unit's output capacity. This avoids delayed judgment of low-load conditions, delays in the outdoor heat exchanger's state switching, and prevents the compressor's discharge pressure Pd from further decreasing below the normal range, thus preventing compressor shutdown and protecting the unit's reliability.

[0069] The air conditioner provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0070] refer to Figure 1 This application provides an air conditioner. The air conditioner includes an outdoor unit 1. The outdoor unit 1 may include a compressor 11. The outdoor unit 1 may include two outdoor heat exchangers. The two outdoor heat exchangers may be a first outdoor heat exchanger 121 and a second outdoor heat exchanger 122, respectively. The outdoor unit 1 may include a first throttling element 131. The outdoor unit 1 may include a second throttling element 132. The first throttling element 131 and the second throttling element 132 may be expansion valves.

[0071] refer to Figure 1 The air conditioner may include at least one indoor unit 2. The indoor unit 2 may include two indoor heat exchangers. The two indoor heat exchangers may be a first indoor heat exchanger 211 and a second indoor heat exchanger 212, respectively.

[0072] refer to Figure 2The outdoor unit 1 may include four commutation devices. The four commutation devices may be a first commutation device 141, a second commutation device 142, a third commutation device 143, and a fourth commutation device 144. Each commutation device has a first interface D, a second interface C, a third interface E, and a fourth interface S.

[0073] The exhaust port of compressor 11 is connected to the first interface D of each of the four reversing devices. The second interface C of the first reversing device 141 is connected to the first outdoor heat exchanger 121. The two sides of the first throttling element 131 are connected to the first outdoor heat exchanger 121 and the first piping 31, respectively.

[0074] The air conditioner includes a first piping 31. The second interface C of the second reversing device 142 is connected to the second outdoor heat exchanger 122. The two sides of the second throttling element 132 are respectively connected to the second outdoor heat exchanger 122 and the first piping 31.

[0075] The air conditioner includes a second piping 32. The two sides of the first indoor heat exchanger 211 are connected to the first piping 31 and the second piping 32, respectively. The air conditioner also includes a third piping 33. The two sides of the second indoor heat exchanger 212 are connected to the first piping 31 and the third piping 33, respectively.

[0076] The second piping 32 is connected to the third interface of the third reversing device 143. The third piping is connected to the third interface of the fourth reversing device 144. The fourth interfaces of all four reversing devices are connected to the air inlet of the compressor 11.

[0077] When the commutator is in the first state, the first and second interfaces are connected, and the third and fourth interfaces are connected. When the commutator is in the second state, the first and third interfaces are connected, and the second and fourth interfaces are connected.

[0078] The third interface of the first commutator is closed. The third interface of the second commutator is closed. The second interface of the third commutator is closed. The second interface of the fourth commutator is closed.

[0079] The system is equipped with four switching devices, which can control the state of these devices to achieve various operating modes. Compared with existing refrigeration systems, it avoids the use of many switching units, simplifies the connection relationship, simplifies the refrigerant flow path, and saves costs. At the same time, it can realize the diversification of air conditioner operating modes, and can ensure that when the outdoor heat exchanger is defrosting, both the first indoor heat exchanger 211 and the second indoor heat exchanger 212 can produce heat, solving the technical problem that the two indoor heat exchangers cannot produce heat at the same time, avoiding excessively low indoor ambient temperature and improving user comfort.

[0080] The reversing device can be a four-way valve. By setting four four-way valves, individual control of the two indoor heat exchangers and the two outdoor heat exchangers can be achieved. This avoids the need for multiple switching units, simplifies the connection, saves costs, and provides good control stability, resulting in high reliability of the refrigeration system and easy maintenance.

[0081] In some embodiments, reference Figure 3 The indoor unit also includes a third throttling element 221 and a fourth throttling element 222. The third throttling element 221 is connected between the first indoor heat exchanger 211 and the first piping 31. The fourth throttling element 222 is connected between the second indoor heat exchanger 212 and the first piping 31. The third throttling element 221 and the fourth throttling element 222 can be expansion valves.

[0082] By incorporating a third and fourth throttling element, and combining the first and second states of the four reversing devices, different refrigerant flow paths can be formed. This enables the air conditioner to operate in multiple modes, including cooling, heating, and reheat dehumidification, solving the technical problem of existing air conditioners having only one operating mode. Furthermore, it allows the air conditioner to simultaneously operate in reheat dehumidification mode and defrosting mode with the outdoor heat exchanger fully heating. This addresses the technical issue in existing three-pipe air conditioners where the indoor heat exchanger of the reheat dehumidification indoor unit cannot fully heat during defrosting of the outdoor heat exchanger, thus preventing excessively low indoor temperatures and improving the user experience.

[0083] In some embodiments, reference Figure 4 The air conditioner has a first mode. This first mode can be the basic cooling mode. When the air conditioner operates in the first mode, all four reversing devices are in the first state. The first indoor heat exchanger 211 and the second indoor heat exchanger 212 are both evaporators, and the first outdoor heat exchanger 121 and the second outdoor heat exchanger 122 are both condensers.

[0084] When the air conditioner is running in the first mode, both the first and second indoor heat exchangers are evaporators, and both the first and second outdoor heat exchangers are condensers, which enables indoor cooling.

[0085] Indoor unit 2 may include an indoor fan. When the air conditioner is operating in the first mode, the indoor fan stops rotating, or the indoor fan rotates to deliver air.

[0086] When the air conditioner is running in the first mode, the refrigerant flow process is as follows:

[0087] The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 11 is divided into two streams. One stream of high-temperature, high-pressure gaseous refrigerant flows into the first outdoor heat exchanger 121 through the first reversing device 141. The first outdoor heat exchanger 121 condenses the high-temperature, high-pressure gaseous refrigerant into a high-pressure, medium-temperature liquid refrigerant. The refrigerant flowing out of the first outdoor heat exchanger 121 flows into the first piping 31 through the first throttling device 131. The other stream of high-temperature, high-pressure gaseous refrigerant flows into the second outdoor heat exchanger 122 through the second reversing device 142. The second outdoor heat exchanger 122 condenses the high-temperature, high-pressure gaseous refrigerant into a high-pressure, medium-temperature liquid refrigerant. The refrigerant flowing out of the second outdoor heat exchanger 122 flows into the first piping 31 through the second throttling device 132.

[0088] The high-pressure, medium-temperature liquid refrigerant flowing out of the first piping 31 is divided into two streams. One stream of high-pressure, medium-temperature liquid refrigerant flows into the third throttling device 221. After being throttled by the third throttling device 221, the refrigerant becomes a low-temperature, low-pressure gas-liquid mixture. This low-temperature, low-pressure gas-liquid mixture flows into the first indoor heat exchanger 211, where it evaporates into a low-temperature, low-pressure gaseous refrigerant. The evaporated refrigerant then flows into the second piping 32. The other stream of high-pressure, medium-temperature liquid refrigerant flows into the fourth throttling device 222. After being throttled by the fourth throttling device 222, the refrigerant becomes a low-temperature, low-pressure gas-liquid mixture. This low-temperature, low-pressure gas-liquid mixture flows into the second indoor heat exchanger 212, where it evaporates into a low-temperature, low-pressure gaseous refrigerant. The evaporated refrigerant then flows into the third piping 33. The refrigerant in the second piping 32 flows back to the compressor 11 via the third reversing device 143, and the refrigerant in the third piping 33 flows back to the compressor 11 via the fourth reversing device 144.

[0089] When the air conditioner is running in the first mode, the first throttling element 131 and the second throttling element 132 are fully open, and the first throttling element 131 and the second throttling element 132 do not throttle the refrigerant, while the third throttling element 221 and the fourth throttling element 222 throttle the refrigerant.

[0090] In some embodiments, reference Figure 5 The air conditioner has a second mode. This second mode can be the basic heating mode. When the air conditioner is operating in the second mode, all four reversing devices are in the second state. The first indoor heat exchanger 211 and the second indoor heat exchanger 212 are both condensers, and the first outdoor heat exchanger 121 and the second outdoor heat exchanger 122 are both evaporators. When the air conditioner is operating in the second mode, the indoor fan either stops rotating or rotates to blow air.

[0091] When the air conditioner is running in the second mode, both the first and second indoor heat exchangers are condensers, and both the first and second outdoor heat exchangers are evaporators, enabling indoor heating.

[0092] When the air conditioner is running in the second mode, the refrigerant flow process is as follows:

[0093] The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 11 is divided into two paths. One path of high-temperature, high-pressure gaseous refrigerant flows into the first indoor heat exchanger 211 through the third reversing device 143 and the second piping 32. The first indoor heat exchanger 211 condenses the high-temperature, high-pressure gaseous refrigerant into a high-pressure, medium-temperature liquid refrigerant. The refrigerant flowing out from the first outdoor heat exchanger 121 flows into the first piping 31 through the third throttling device 221. The other path of high-temperature, high-pressure gaseous refrigerant flows into the second indoor heat exchanger 212 through the fourth reversing device 144 and the third piping 33. The second indoor heat exchanger 212 condenses the high-temperature, high-pressure gaseous refrigerant into a high-pressure, medium-temperature liquid refrigerant. The refrigerant flowing out from the second outdoor heat exchanger 122 flows into the first piping 31 through the fourth throttling device 222.

[0094] The refrigerant flowing out of the first piping 31 is split into two paths. One path flows into the first throttling element 131, where it becomes a low-temperature, low-pressure gas-liquid mixture. This mixture then flows into the first outdoor heat exchanger 121, where it evaporates into a low-temperature, low-pressure gaseous refrigerant. The evaporated refrigerant then flows back to the compressor 11 via the first reversing device 141. The other path flows into the second throttling element 132, where it becomes a low-temperature, low-pressure gas-liquid mixture. This mixture then flows into the second outdoor heat exchanger 122, where it evaporates into a low-temperature, low-pressure gaseous refrigerant. The evaporated refrigerant then flows back to the compressor 11 via the second reversing device 142. When the air conditioner is running in the second mode, the first throttling element 131 and the second throttling element 132 throttle the airflow.

[0095] In some embodiments, the indoor unit 2 has an indoor air outlet. The first indoor heat exchanger 211 is located on the side of the second indoor heat exchanger 212 near the indoor air outlet.

[0096] Indoor unit 2 has an indoor unit casing. An indoor air outlet is located on the indoor unit casing. A first indoor heat exchanger 211 and a second indoor heat exchanger 212 are located inside the indoor unit casing. Indoor unit 2 also has an indoor air inlet, located on the indoor unit casing. Air enters indoor unit 2 through the indoor air inlet, first exchanges heat with the second indoor heat exchanger 212, then exchanges heat with the first indoor heat exchanger 211, and finally exits indoor unit 2 through the indoor air outlet.

[0097] refer to Figure 6The air conditioner has a third mode. The third mode can be a basic reheat dehumidification mode. When the air conditioner is running in the third mode, the first commutator 141, the second commutator 142 and the fourth commutator 144 are all in the first state, the third commutator 143 is in the second state, the first indoor heat exchanger 211, the first outdoor heat exchanger 121 and the second outdoor heat exchanger 122 are all condensers, and the second indoor heat exchanger 212 is an evaporator.

[0098] The basic reheat dehumidification mode is also commonly known as the comfort mode. When the air conditioner is running in the third mode, the first indoor heat exchanger, the first outdoor heat exchanger, and the second outdoor heat exchanger act as condensers, while the second indoor heat exchanger acts as an evaporator. The air entering the indoor unit 2 first passes through the second indoor heat exchanger 212 for cooling and dehumidification, and then passes through the first indoor heat exchanger 211 for heating. This ensures that the outlet air temperature is dry without being excessively cold, improving user comfort. It is suitable for user scenarios where users cannot tolerate cold air.

[0099] When the air conditioner is running in the third mode, the refrigerant flow process is as follows:

[0100] The high-temperature, high-pressure gaseous refrigerant discharged from compressor 11 is divided into three streams. The first stream of high-temperature, high-pressure gaseous refrigerant flows into the first outdoor heat exchanger 121 via the first reversing device 141. The first outdoor heat exchanger 121 condenses the high-temperature, high-pressure gaseous refrigerant into a high-pressure, medium-temperature liquid refrigerant. The refrigerant flowing out of the first outdoor heat exchanger 121 flows into the first piping 31 via the first throttling device 131. The second stream of high-temperature, high-pressure gaseous refrigerant flows into the second outdoor heat exchanger 122 via the second reversing device 142. The second outdoor heat exchanger 122 condenses the high-temperature, high-pressure gaseous refrigerant into a high-pressure, medium-temperature liquid refrigerant. The refrigerant flowing out of the second outdoor heat exchanger 122 flows into the first piping 31 via the second throttling device 132. The third stream of high-temperature... High-pressure gaseous refrigerant enters the first indoor heat exchanger 211 via the third reversing device 143 and the second piping 32. The first indoor heat exchanger 211 condenses the high-temperature and high-pressure gaseous refrigerant into a high-pressure and medium-temperature liquid refrigerant. The refrigerant flowing out of the first indoor heat exchanger 211 merges with the refrigerant in the first piping 31 via the first throttling device 131 and then flows into the fourth throttling device 222. After being throttled by the fourth throttling device 222, the refrigerant becomes a low-temperature and low-pressure gas-liquid mixture. The low-temperature and low-pressure gas-liquid mixture flows into the second indoor heat exchanger 212. The second indoor heat exchanger 212 evaporates the low-temperature and low-pressure gas-liquid mixture into a low-temperature and low-pressure gaseous refrigerant. The evaporated refrigerant flows back to the compressor 11 via the third piping 33.

[0101] When the air conditioner is running in the third mode, the first throttling element 131 and the second throttling element 132 are fully open.

[0102] In some embodiments, when the first outdoor heat exchanger 121 and the second outdoor heat exchanger 122 are used as evaporators and the outdoor ambient temperature is low and the humidity is high, frost will form on the surfaces of the first outdoor heat exchanger 121 and the second outdoor heat exchanger 122. When the amount of frost accumulates to a certain extent, defrosting operation is required to avoid affecting the heating of the indoor unit.

[0103] refer to Figure 8 The air conditioner has a fourth mode. This fourth mode can be a continuous heating and defrosting mode. When the air conditioner is operating in the fourth mode, it defrosts the first outdoor heat exchanger 121. In this mode, the first commutator 141 is in its first state, while the second commutator 142, third commutator 143, and fourth commutator 144 are all in their second states. The first outdoor heat exchanger 121, the first indoor heat exchanger 211, and the second indoor heat exchanger 212 are all condensers, and the second outdoor heat exchanger 122 is an evaporator.

[0104] Setting up a fourth mode allows the second outdoor heat exchanger 122 to continue functioning as an evaporator while the first outdoor heat exchanger 121 is defrosting, compared to the traditional method of changing the refrigerant flow direction to defrost the outdoor heat exchanger. This enables the first indoor heat exchanger 211 and the second indoor heat exchanger 212 to continuously provide heating, increasing the indoor air temperature during defrosting, preventing excessively low indoor temperatures, and improving user comfort. Furthermore, since the indoor heat exchangers all function as condensers during defrosting, the heating capacity of the indoor unit 2 recovers more quickly after defrosting. Compared to the traditional method of changing the refrigerant flow direction to defrost the outdoor heat exchanger, the indoor temperature fluctuates less and recovers faster.

[0105] When the air conditioner is running in the fourth mode, the refrigerant flow process is as follows:

[0106] The high-temperature, high-pressure gaseous refrigerant discharged from compressor 11 is divided into three streams. The first stream of high-temperature, high-pressure gaseous refrigerant flows into the first indoor heat exchanger via the third reversing device 143 and the second piping 32. The first indoor heat exchanger 211 condenses the high-temperature, high-pressure gaseous refrigerant into a high-pressure, medium-temperature liquid refrigerant. The refrigerant flowing out of the first indoor heat exchanger 211 flows into the first piping 31 via the third throttling device 221. The second stream of high-temperature, high-pressure gaseous refrigerant flows into the second indoor heat exchanger via the fourth reversing device 144 and the third piping 33. The second indoor heat exchanger 212 condenses the high-temperature, high-pressure gaseous refrigerant into a high-pressure, medium-temperature liquid refrigerant. The refrigerant flowing out of the second indoor heat exchanger flows into the first piping 31 via the fourth throttling device 222. The third stream of high-temperature, high-pressure gaseous refrigerant flows into the first piping 31 via the fourth throttling device 222. The first reversing device 141 directs the flow of refrigerant into the first outdoor heat exchanger 121 for condensation to defrost the first outdoor heat exchanger 121. The first outdoor heat exchanger 121 condenses the high-temperature, high-pressure gaseous refrigerant into a high-pressure, medium-temperature liquid refrigerant. The refrigerant flowing out of the first outdoor heat exchanger 121 merges with the refrigerant in the first piping 31 via the first throttling device 131. The merged refrigerant flows into the second throttling device 132, where it is throttled into a low-temperature, low-pressure gas-liquid mixture. This low-temperature, low-pressure gas-liquid mixture flows into the second outdoor heat exchanger 122, where it evaporates back into a low-temperature, low-pressure gaseous refrigerant. The evaporated refrigerant then flows back to the compressor 11 via the second reversing device 142. When the air conditioner is operating in the fourth mode, the first throttling device 131 is fully open, and the second throttling device 132 throttles the flow.

[0107] In some embodiments, reference Figure 7 The air conditioner has a fifth mode. The fifth mode can be a continuous heating and defrosting mode, in which the air conditioner defrosts the second outdoor heat exchanger 122 when it is running in the fifth mode.

[0108] When the air conditioner is running in the fifth mode, the first commutator 141 is in the first state, the second commutator 142, the third commutator 143 and the fourth commutator 144 are all in the second state, the second outdoor heat exchanger 122, the first indoor heat exchanger 211 and the second indoor heat exchanger 212 are all condensers, and the first outdoor heat exchanger 121 is an evaporator.

[0109] The fifth mode, which works in conjunction with the fourth mode, enables alternating defrosting of the first outdoor heat exchanger 121 and the second outdoor heat exchanger 122. This allows the first outdoor heat exchanger 121 to continue functioning as an evaporator while the second outdoor heat exchanger 122 is defrosting, ensuring continuous heating for both the first indoor heat exchanger 211 and the second indoor heat exchanger 212. This increases the indoor air temperature during defrosting, improving user comfort. Furthermore, since the indoor heat exchangers function as condensers during defrosting, the heating capacity of the indoor unit 2 recovers more quickly after defrosting. Compared to reverse defrosting, indoor temperature fluctuations are smaller, and indoor temperature recovery is faster.

[0110] When the air conditioner is running in the fifth mode, the refrigerant flow process is as follows:

[0111] The high-temperature, high-pressure gaseous refrigerant discharged from compressor 11 is divided into three streams. The first stream of high-temperature, high-pressure gaseous refrigerant flows into the first indoor heat exchanger via the third reversing device 143 and the second piping 32. The first indoor heat exchanger 211 condenses the high-temperature, high-pressure gaseous refrigerant into a high-pressure, medium-temperature liquid refrigerant. The refrigerant flowing out of the first indoor heat exchanger 211 flows into the first piping 31 via the third throttling device 221. The second stream of high-temperature, high-pressure gaseous refrigerant flows into the second indoor heat exchanger via the fourth reversing device 144 and the third piping 33. The second indoor heat exchanger 212 condenses the high-temperature, high-pressure gaseous refrigerant into a high-pressure, medium-temperature liquid refrigerant. The refrigerant flowing out of the second indoor heat exchanger flows into the first piping 31 via the fourth throttling device 222. The third stream of high-temperature, high-pressure gaseous refrigerant flows into the first piping 31 via the fourth throttling device 222. The refrigerant flowing into the second outdoor heat exchanger 122 via the second reversing device 142 is condensed to defrost the second outdoor heat exchanger 122. The second outdoor heat exchanger 122 condenses the high-temperature, high-pressure gaseous refrigerant into a high-pressure, medium-temperature liquid refrigerant. The refrigerant flowing out of the second outdoor heat exchanger 122 merges with the refrigerant in the first piping 31 via the second throttling device 132. The merged refrigerant flows into the first throttling device 131, where it is throttled into a low-temperature, low-pressure gas-liquid mixture. This low-temperature, low-pressure gas-liquid mixture flows into the first outdoor heat exchanger 121, where it evaporates back into a low-temperature, low-pressure gaseous refrigerant. The evaporated refrigerant then flows back to the compressor 11 via the first reversing device 141. When the air conditioner is operating in the fifth mode, the second throttling device 132 is fully open, and the first throttling device 131 is throttling.

[0112] In some embodiments, reference Figure 1 The outdoor unit 1 includes a gas-liquid separator 15. The fourth interface S of the four reversing devices is connected to the inlet of the gas-liquid separator 15. The outlet of the gas-liquid separator 15 is connected to the air inlet of the compressor 11.

[0113] Outdoor unit 1 includes a first shut-off valve 161. The first shut-off valve 161 is connected to the first piping 31 to control the opening and closing of the first piping 31. Outdoor unit 1 includes a second shut-off valve 162. The first shut-off valve 161 can be referred to as a liquid pipe shut-off valve. The second shut-off valve 162 is connected to the second piping 32 to control the opening and closing of the second piping 32. Outdoor unit 1 includes a third shut-off valve 163. The third shut-off valve 163 is located on the third piping 33 to control the opening and closing of the third piping 33.

[0114] In some embodiments, the outdoor unit 1 includes an outdoor fan. The outdoor fan rotates when the air conditioner is operating in a first mode. The outdoor fan rotates when the air conditioner is operating in a second mode. The outdoor fan rotates when the air conditioner is operating in a third mode. The outdoor fan rotates when the air conditioner is operating in a fourth mode. The outdoor fan rotates when the air conditioner is operating in a fifth mode.

[0115] In some embodiments, reference Figure 1 The outdoor unit 1 includes two outdoor fans. The two outdoor fans are a first outdoor fan 171 and a second outdoor fan 172. The first outdoor fan 171 is adapted to the first outdoor heat exchanger 121, and the second outdoor fan 172 is adapted to the second outdoor heat exchanger 122.

[0116] When the air conditioner is running in the first mode, both the first outdoor fan 171 and the second outdoor fan 172 rotate. When the air conditioner is running in the second mode, both the first outdoor fan 171 and the second outdoor fan 172 rotate. When the air conditioner is running in the third mode, both the first outdoor fan 171 and the second outdoor fan 172 rotate.

[0117] When the air conditioner is running in the fourth mode, the first outdoor fan 171 is stationary, while the second outdoor fan 172 rotates. Setting the first outdoor fan to be stationary and the second outdoor fan to rotate in the fourth mode ensures the heat exchange efficiency of the second outdoor heat exchanger and reduces heat exchange between the first outdoor heat exchanger and the outdoor environment, thus improving the defrosting effect of the first outdoor heat exchanger.

[0118] When the air conditioner is running in mode 5, the first outdoor fan 171 rotates while the second outdoor fan 172 remains stationary. Setting the first outdoor fan to rotate and the second outdoor fan to remain stationary in mode 5 ensures the heat exchange efficiency of the first outdoor heat exchanger and reduces heat exchange between the second outdoor heat exchanger and the outdoor environment, thus improving the defrosting effect of the second outdoor heat exchanger. Table 1 shows the status of the four commutation devices and two outdoor fans when the air conditioner is running in different modes.

[0119] Table 1

[0120] model First Mode Second Mode Third Mode Fourth Mode Fifth Mode First commutation device First state Second state First state First state Second state Second commutation device First state Second state First state Second state First state Third commutation device First state Second state Second state Second state Second state Fourth commutation device First state Second state First state Second state Second state First outdoor fan Rotation Rotation Rotation still Rotation Second outdoor fan Rotation Rotation Rotation Rotation still

[0121] In some embodiments, reference Figure 3 The indoor unit may include a first switching device 231, a second switching device 232, and a third switching device 233. The first switching device may be connected between the first piping 31 and the third throttling element 221 and the fourth throttling element 222. The second switching device 232 may be connected between the first indoor heat exchanger and the second piping. The third switching device may be connected between the third piping and the second indoor heat exchanger. The first switching device 231, the second switching device 232, and the third switching device 233 may be solenoid valves.

[0122] The first switch device 231, the second switch device 232, and the third switch device 233 are provided to control the on / off state of both sides of the first and second indoor heat exchangers, which is convenient for control and can realize multiple refrigerant flow paths.

[0123] In some embodiments, the air conditioner includes a controller. The controller is connected to the compressor. The controller is connected to an indoor fan. The controller is connected to an outdoor fan.

[0124] The controller is connected to the commutator. The controller controls the commutator to switch between a first state and a second state. When the controller controls the commutator to switch to the first state, the first and second interfaces are connected, and the third and fourth interfaces are connected; when the controller controls the commutator to switch to the second state, the first and third interfaces are connected, and the second and fourth interfaces are connected.

[0125] The system is equipped with a controller and four reversing devices. The controller controls each reversing device to switch between a first state and a second state. By controlling the states of the four reversing devices, different refrigerant flow paths can be formed, enabling multiple different operating modes. Compared with existing refrigeration systems, this system avoids the use of many switching units, simplifies the connection relationship, simplifies the refrigerant flow path, and saves costs. At the same time, it enables diversified air conditioner operating modes and allows both the first and second indoor heat exchangers to heat while the outdoor heat exchanger is defrosting, solving the technical problem that the two indoor heat exchangers cannot heat at the same time, avoiding excessively low indoor ambient temperatures, and improving user comfort.

[0126] In some embodiments, low-load operating conditions typically occur in scenarios such as: fewer than two indoor units are turned on by the user; the difference between the outdoor ambient temperature and the set target temperature is small, and the difference between the indoor ambient temperature and the set target temperature is also small. For example, during cooling: outdoor ambient temperature 20°C, indoor ambient temperature 20°C, set target temperature 18°C; during heating: outdoor ambient temperature 20°C, indoor ambient temperature 20°C, set target temperature 22°C. Extreme operating conditions: for example, cooling with an outdoor ambient temperature of -5°C and an indoor ambient temperature of 20°C, and heating with an outdoor ambient temperature of 20°C and an indoor ambient temperature of 32°C.

[0127] Under non-extreme operating conditions, when a low-load condition occurs, the compressor 11 will reduce its frequency and the outdoor fan will reduce its speed to reduce the output capacity of the outdoor unit 1. However, the frequency of the compressor 11 and the speed of the outdoor fan cannot be reduced indefinitely, so the output capacity of the outdoor unit 1 is still relatively large. Moreover, the judgment of low-load conditions is relatively lagging, and timely adjustment cannot be made, which will cause the compressor 11 to stop frequently, resulting in large fluctuations in indoor ambient temperature and causing the indoor air outlet temperature to be too low or too high, affecting the user's comfort. In addition, under extreme operating conditions, the air conditioner may fail to operate. For example, when the outdoor ambient temperature is low and the air conditioner is cooling, the excessive condensing capacity of the outdoor heat exchanger may cause the pressure on the high-pressure side of the compressor 11 to fall below its operating pressure range, causing the air conditioner to shut down and affecting user operation. Alternatively, low pressure on the high-pressure side of the compressor 11 may result in low evaporation temperature, causing the air conditioner to frequently start and stop the compressor 11 to prevent the indoor unit 2 from freezing, which is detrimental to the reliability of the compressor 11's operation. For example, when the indoor ambient temperature is high and the air conditioner is heating, the excessive evaporation capacity of the outdoor heat exchanger may lead to high evaporation pressure, which in turn leads to high condensation pressure, exceeding the operating pressure range of the compressor 11 and causing the compressor 11 to fail to operate, affecting user operation.

[0128] The air conditioner may include a first pressure detection device 41. The first pressure detection device 41 is used to detect the discharge pressure of the compressor 11. The first pressure detection device 41 may be a pressure sensor. The air conditioner may also include a controller. The controller is connected to the first pressure detection device 41.

[0129] refer to Figure 9 The controller is configured to switch one of the two outdoor heat exchangers to evaporator operation when both the first indoor heat exchanger 211 and the second indoor heat exchanger 212 are operating as evaporators and both outdoor heat exchangers are operating as condensers. If the operating frequency H of the compressor 11 is equal to the minimum frequency Hmin of the compressor 11, the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, and the discharge pressure Pd of the compressor 11 is less than the preset discharge pressure Pdmin, then one of the two outdoor heat exchangers will be switched to evaporator operation.

[0130] When operating in basic cooling mode, once the operating frequency H of compressor 11 equals the minimum frequency Hmin of compressor 11 and the speed N of the outdoor fan equals the minimum speed Nmin of the outdoor fan, the compressor frequency and outdoor fan speed cannot be further reduced. If the output capacity of the outdoor unit is still relatively high, the discharge pressure of the compressor will first decrease to the minimum allowable value compared with the suction pressure of the compressor. Therefore, the discharge pressure Pd of compressor 11 is set to be compared with the preset discharge pressure Pdmin. When the discharge pressure Pd of compressor 11 is less than the preset discharge pressure Pdmin, one of the outdoor heat exchangers is controlled to switch to evaporator, reducing the heat exchange area of ​​the outdoor heat exchanger and reducing the output capacity of the outdoor unit. This avoids the situation of delayed judgment of low load conditions, avoids the state switching lag of the outdoor heat exchanger, avoids the discharge pressure Pd of compressor 11 from further decreasing to below the normal range of compressor discharge pressure, avoids compressor shutdown, and protects the reliability of the unit.

[0131] In some embodiments, the air conditioner includes a first temperature detection device 42. The first temperature detection device 42 is used to detect the return air temperature Ti of the indoor unit 2. The first temperature detection device 42 is connected to the controller. The first temperature detection device 42 is a temperature sensor.

[0132] In some embodiments, reference Figure 9 The controller is configured such that when both the first indoor heat exchanger 211 and the second indoor heat exchanger 212 are operating as evaporators and both outdoor heat exchangers are operating as condensers, if the operating frequency H of the compressor 11 is equal to the minimum frequency Hmin of the compressor 11, the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, the discharge pressure of the compressor 11 is greater than or equal to the preset discharge pressure Pdmin, and the difference between the return air temperature Ti of the indoor unit 2 and the set target temperature Ts is less than the first set value, then one of the two outdoor heat exchangers will be switched to evaporator operation. This can reduce the heat exchange area of ​​the outdoor heat exchanger, reduce the output capacity of the outdoor unit, avoid frequent compressor start-stop due to the small difference between the return air temperature Ti of the indoor unit 2 and the set target temperature Ts, and improve the service life of the compressor.

[0133] In some embodiments, the controller is configured to:

[0134] When both the first indoor heat exchanger 211 and the second indoor heat exchanger 212 are operating as evaporators, and the two outdoor heat exchangers are operating as evaporators and condensers respectively, if the increase in compressor frequency demanded by the air conditioner ΔH is greater than the second set value, the outdoor heat exchanger operating as an evaporator will be switched to condenser operation. This allows for real-time monitoring of the air conditioner's status and timely adjustment of the outdoor unit's output capacity to meet the needs of the indoor unit when the demand increases.

[0135] In some embodiments, the indoor unit 2 is provided with an indoor air outlet. The first indoor heat exchanger 211 is located on the side of the second indoor heat exchanger 212 near the indoor air outlet.

[0136] In some embodiments, the air conditioner includes a second temperature detection device 43. The second temperature detection device 43 is used to detect the outlet air temperature To of the indoor unit 2. The second temperature detection device 43 is connected to the controller. The second temperature detection device 43 can be a temperature sensor.

[0137] refer to Figure 10 The controller is configured as follows:

[0138] When both the first indoor heat exchanger 211 and the second indoor heat exchanger 212 are operating as evaporators, and the two outdoor heat exchangers are operating as evaporators and condensers respectively, if the increase in compressor frequency required by the air conditioner ΔH is less than or equal to the second set value and the outlet air temperature To of the indoor unit 2 is less than the third preset value, the first indoor heat exchanger 211 will be switched to condenser operation. This can reduce the heat exchange area of ​​the indoor heat exchanger, reduce the output of cooling capacity, and avoid discomfort caused by excessively low indoor outlet air temperature.

[0139] In some embodiments, reference Figure 10 The controller is configured to: when both the first indoor heat exchanger 211 and the second indoor heat exchanger 212 are operating as evaporators, and the two outdoor heat exchangers are operating as evaporators and condensers respectively, if the increase in compressor frequency required by the air conditioner ΔH is less than or equal to the second preset value, the outlet air temperature To of the indoor unit 2 is greater than or equal to the third preset value, and the difference between the return air temperature Ti of the indoor unit 2 and the set target temperature Ts is less than the fourth preset value, then the first indoor heat exchanger 211 will be switched to condenser operation. This will increase the heat exchange area of ​​the indoor heat exchanger, reduce the output of cooling capacity, and prevent the compressor from frequently starting and stopping due to the small difference between the return air temperature Ti of the indoor unit 2 and the set target temperature Ts, thereby improving the service life of the compressor.

[0140] In some embodiments, the controller is configured to:

[0141] When the first indoor heat exchanger 211 operates as a condenser, the second indoor heat exchanger 212 operates as an evaporator, and the two outdoor heat exchangers operate as an evaporator and a condenser respectively, if the increase in compressor frequency demanded by the air conditioner ΔH is greater than the fifth set value, the first indoor heat exchanger 211 will be switched to evaporator operation. This allows for real-time monitoring of the air conditioner's status and timely adjustment of the indoor unit's cooling capacity output when the demand increases, thus meeting the cooling needs of the indoor unit.

[0142] In some embodiments, reference Figure 14 The controller performs the following steps:

[0143] S10: The air conditioner is operating in basic cooling mode;

[0144] S11: The first indoor heat exchanger 211 and the second indoor heat exchanger 212 both operate as evaporators, and both outdoor heat exchangers both operate as condensers.

[0145] S12: Determine whether the operating frequency H of compressor 11 is equal to the minimum frequency Hmin of compressor 11 and whether the speed N of outdoor fan is equal to the minimum speed Nmin of outdoor fan. If not, proceed to step S11. If yes, determine whether the exhaust pressure Pd of compressor 11 is less than the preset exhaust pressure Pdmin. If yes, proceed to step S13. If no, determine whether the difference between the return air temperature Ti of indoor unit 2 and the set target temperature Ts is less than the first set value. If yes, proceed to step S13. If no, proceed to step S11.

[0146] S13: The first indoor heat exchanger 211 and the second indoor heat exchanger 212 both operate as evaporators, and the two outdoor heat exchangers operate as evaporators and condensers, respectively.

[0147] S14: Determine whether the increase in compressor frequency ΔH required by the air conditioner is greater than the second set value. If yes, proceed to step S11. If no, determine whether the outlet air temperature To of indoor unit 2 is less than the third preset value. If yes, proceed to step S15. If no, determine whether the difference between the return air temperature Ti of indoor unit 2 and the set target temperature Ts is less than the fourth set value. If yes, proceed to step S15. If no, proceed to step S13.

[0148] S15: The first indoor heat exchanger 211 operates as a condenser, the second indoor heat exchanger 212 operates as an evaporator, and the two outdoor heat exchangers operate as an evaporator and a condenser, respectively.

[0149] S16: Determine whether the increase in compressor frequency demanded by the air conditioner, ΔH, is greater than the fifth set value. If yes, proceed to step S13; otherwise, proceed to S15.

[0150] Pdmin can be any value between 1.0MPa and 1.2MPa. The first setting can be any value between -2℃ and 2℃. The second setting can be any value between 10Hz and 20Hz. The third preset value can be any value between 5℃ and 8℃. The fourth setting can be any value between -2℃ and 2℃. The fifth setting can be any value between 10Hz and 20Hz.

[0151] The basic cooling mode is as follows: the first indoor heat exchanger 211 operates as an evaporator, the second indoor heat exchanger 212 operates as an evaporator, and both outdoor heat exchangers operate as condensers. The first low-load cooling mode is as follows: both the first indoor heat exchanger 211 and the second indoor heat exchanger 212 operate as evaporators, and the two outdoor heat exchangers operate as evaporators and condensers, respectively. The second low-load cooling mode is as follows: the first indoor heat exchanger 211 operates as a condenser, the second indoor heat exchanger 212 operates as an evaporator, and the two outdoor heat exchangers operate as evaporators and condensers, respectively. Table 2 shows the operating status of the two indoor and two outdoor heat exchangers under different operating modes.

[0152] Table 2

[0153]

[0154] When the air conditioner is running in the first mode of low cooling load, the first commutator 141 is in the second state, and the second commutator 142, the third commutator 143 and the fourth commutator 144 are in the first state; or, the second commutator 142 is in the second state, and the first commutator 141, the third commutator 143 and the fourth commutator 144 are in the first state.

[0155] When the air conditioner is running in the second mode of low cooling load, the first commutator 141 and the third commutator 143 are in the second state, and the second commutator 142 and the fourth commutator 144 are in the first state; or, the second commutator 142 and the third commutator 143 are in the second state, and the first commutator 141 and the fourth commutator 144 are in the first state.

[0156] Since low load typically occurs when only one indoor unit 2 is running, taking the operation of one indoor unit 2 as an example, see below. Figure 9 and attached Figure 10 The refrigerant flow paths are displayed for the first mode and the second mode of low-load cooling, respectively.

[0157] In some embodiments, the air conditioner includes a second pressure detection device 44. The second pressure detection device 44 is used to detect the suction pressure of the compressor 11. The second pressure detection device 44 is connected to the controller. The second pressure detection device 44 can be a pressure sensor.

[0158] refer to Figure 11The controller is configured to switch one of the two outdoor heat exchangers to condenser operation when both the first indoor heat exchanger 211 and the second indoor heat exchanger 212 are operating as condensers and both outdoor heat exchangers are operating as evaporators. If the operating frequency H of the compressor 11 is equal to the minimum frequency Hmin of the compressor 11, the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, and the suction pressure Ps of the compressor 11 is greater than the preset suction pressure Psmax, then one of the two outdoor heat exchangers will be switched to condenser operation.

[0159] When operating in basic heating mode, once the operating frequency of compressor 11 equals its minimum frequency Hmin and the speed of the outdoor fan equals its minimum speed Nmin, the compressor frequency and outdoor fan speed cannot be further reduced. If the output capacity of the outdoor unit is still relatively high, the compressor's suction pressure will first rise to the maximum allowable suction pressure compared to the compressor's discharge pressure. Therefore, when the suction pressure Ps of compressor 11 is set to be greater than the preset suction pressure Psmax, one of the outdoor heat exchangers is controlled to switch to evaporator operation, reducing the heat exchange area of ​​the outdoor heat exchanger and reducing the output capacity of the outdoor unit. This avoids delayed judgment of low-load conditions, delays the state switching of the outdoor heat exchanger, and prevents the suction pressure Ps of compressor 11 from further increasing to exceed the normal range of compressor suction pressure, thus preventing compressor shutdown and protecting the reliability of the unit.

[0160] In some embodiments, reference Figure 11 The controller is configured such that when both the first indoor heat exchanger 211 and the second indoor heat exchanger 212 are operating as condensers, and both outdoor heat exchangers are operating as evaporators, if the operating frequency H of the compressor 11 is equal to the minimum frequency Hmin of the compressor 11, the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, the suction pressure Ps of the compressor 11 is less than or equal to the preset discharge pressure Psmax, and the difference between the set target temperature Ts and the return air temperature Ti of the indoor unit 2 is less than the sixth set value, then one of the two outdoor heat exchangers will be switched to condenser operation. This can reduce the heat exchange area of ​​the outdoor heat exchanger, reduce the output capacity of the outdoor unit, avoid frequent compressor start-stop due to the small difference between the set target temperature Ts and the return air temperature Ti of the indoor unit 2, and improve the service life of the compressor.

[0161] In some embodiments, the controller is configured to:

[0162] When both the first indoor heat exchanger 211 and the second indoor heat exchanger 212 are operating as condensers, and the two outdoor heat exchangers are operating as evaporators and condensers respectively, if the increase in compressor frequency demanded by the air conditioner ΔH is greater than the seventh set value, the outdoor heat exchanger operating as a condenser will be switched to evaporator operation. This allows for real-time monitoring of the air conditioner's status and timely adjustment of the outdoor unit's output capacity to meet the needs of the indoor unit when the demand increases.

[0163] In some embodiments, reference Figure 12 The controller is configured as follows:

[0164] When both the first indoor heat exchanger 211 and the second indoor heat exchanger 212 are operating as condensers, and the two outdoor heat exchangers are operating as evaporators and condensers respectively, if the increase in compressor frequency required by the air conditioner ΔH is less than or equal to the seventh preset value and the air outlet temperature To of the indoor unit 2 is greater than the eighth preset value, the first indoor heat exchanger 211 will be switched to evaporator operation. This can reduce the heat exchange area of ​​the indoor heat exchanger, reduce heat output, and avoid discomfort caused by excessively high indoor air outlet temperature.

[0165] In some embodiments, reference Figure 12 The controller is configured to: when both the first indoor heat exchanger 211 and the second indoor heat exchanger 212 are operating as condensers, and the two outdoor heat exchangers are operating as evaporators and condensers respectively, if the increase in compressor frequency required by the air conditioner ΔH is less than or equal to the seventh preset value, the outlet air temperature To of the indoor unit 2 is less than or equal to the eighth preset value, and the difference between the set target temperature Ts and the return air temperature Ti of the indoor unit 2 is less than the ninth preset value, then the first indoor heat exchanger 211 will be switched to evaporator operation. This will increase the heat exchange area of ​​the indoor heat exchanger, reduce heat output, and prevent the compressor from frequently starting and stopping due to the small difference between the set target temperature Ts and the return air temperature Ti of the indoor unit 2, thereby improving the service life of the compressor.

[0166] In some embodiments, the controller is configured to:

[0167] When the first indoor heat exchanger 211 operates as an evaporator, the second indoor heat exchanger 212 operates as a condenser, and the two outdoor heat exchangers operate as evaporators and condensers respectively, if the increase in compressor frequency demanded by the air conditioner ΔH is greater than the eleventh set value, the first indoor heat exchanger 211 will be switched to condenser operation. This allows for real-time monitoring of the air conditioner's status and timely adjustment of the indoor unit's heat output capacity to meet the indoor unit's heat requirements when demand increases.

[0168] In some embodiments, reference Figure 15 The controller performs the following steps:

[0169] S20: Air conditioner operates in basic heating mode;

[0170] S21: The first indoor heat exchanger 211 and the second indoor heat exchanger 212 both operate as condensers, and both outdoor heat exchangers both operate as evaporators.

[0171] S22: Determine whether the operating frequency H of compressor 11 is equal to the minimum frequency Hmin of compressor 11 and whether the speed N of outdoor fan is equal to the minimum speed Nmin of outdoor fan. If not, proceed to step S21. If yes, determine whether the suction pressure Ps of compressor 11 is greater than the preset suction pressure Psmax. If yes, proceed to step S23. If no, determine whether the difference between the set target temperature Ts and the return air temperature Ti of indoor unit 2 is less than the sixth set value. If yes, proceed to step S23. If no, proceed to step S21.

[0172] S23: The first indoor heat exchanger 211 and the second indoor heat exchanger 212 both operate as condensers, and the two outdoor heat exchangers operate as evaporators and condensers, respectively.

[0173] S24: Determine whether the increase in compressor frequency ΔH required by the air conditioner is greater than the seventh set value. If yes, proceed to step S21. If no, determine whether the outlet air temperature To of indoor unit 2 is greater than the eighth preset value. If yes, proceed to step S25. If no, determine whether the difference between the set target temperature Ts and the return air temperature Ti of indoor unit 2 is less than the ninth set value. If yes, proceed to step S25. If no, proceed to step S23.

[0174] S25: The first indoor heat exchanger 211 operates as an evaporator, the second indoor heat exchanger 212 operates as a condenser, and the two outdoor heat exchangers operate as an evaporator and a condenser, respectively.

[0175] S26: Determine whether the increase in compressor frequency required by the air conditioner, ΔH, is greater than the eleventh set value. If yes, proceed to step S23; otherwise, proceed to S25.

[0176] Pdmax can be any value between 1.6MPa and 1.8MPa. The sixth setting can be any value between -2℃ and 2℃.

[0177] The seventh setting can be any value between 10Hz and 20Hz. The eighth preset value can be any value between 45℃ and 50℃.

[0178] The ninth setting can be any value between -2℃ and 2℃. The eleventh setting can be any value between 10Hz and 20Hz.

[0179] The basic heating mode is as follows: the first indoor heat exchanger 211 operates as a condenser, the second indoor heat exchanger 212 operates as a condenser, and both outdoor heat exchangers operate as evaporators. The first low-load heating mode is as follows: both the first indoor heat exchanger 211 and the second indoor heat exchanger 212 operate as condensers, and the two outdoor heat exchangers operate as evaporators and condensers, respectively. The second low-load heating mode is as follows: the first indoor heat exchanger 211 operates as an evaporator, the second indoor heat exchanger 212 operates as a condenser, and the two outdoor heat exchangers operate as evaporators and condensers, respectively.

[0180] When the air conditioner is operating in the first mode of low-load heating, the first commutator 141 is in the first state, and the second commutator 142, the third commutator 143 and the fourth commutator 144 are in the second state; or, the second commutator 142 is in the first state, and the first commutator 141, the third commutator 143 and the fourth commutator 144 are in the second state.

[0181] When the air conditioner is running in the second mode of low-load heating, the first commutator 141 and the third commutator 143 are in the first state, and the second commutator 142 and the fourth commutator 144 are in the second state; or, the second commutator 142 and the third commutator 143 are in the first state, and the first commutator 141 and the fourth commutator 144 are in the second state.

[0182] Since low load typically occurs when only one indoor unit 2 is running, taking the operation of one indoor unit 2 as an example, see below. Figure 11 and attached Figure 12 The refrigerant flow paths are displayed for the first and second modes of low-load heating, respectively.

[0183] In some embodiments, reference Figure 13 The controller is configured as follows:

[0184] When the first indoor heat exchanger 211 operates as a condenser, the second indoor heat exchanger 212 operates as an evaporator, and both outdoor heat exchangers operate as condensers, if the operating frequency H of the compressor 11 is equal to the minimum frequency of the compressor 11, the speed N of the outdoor fan is equal to the minimum speed of the outdoor fan, and the discharge pressure Pd of the compressor 11 is less than the preset discharge pressure Pdmin, then one of the two outdoor heat exchangers will be switched to evaporator operation.

[0185] When operating in basic reheat dehumidification mode, after the operating frequency of compressor 11 equals the minimum frequency Hmin of compressor 11 and the speed of outdoor fan equals the minimum speed Nmin of outdoor fan, the compressor frequency and outdoor fan speed cannot be further reduced. If the output capacity of the outdoor unit is still relatively high, the compressor discharge pressure will first decrease to the minimum allowable value compared with the compressor suction pressure. Therefore, the discharge pressure Pd of compressor 11 is set to be compared with the preset discharge pressure Pdmin. When the discharge pressure Pd of compressor 11 is less than the preset discharge pressure Pdmin, one of the outdoor heat exchangers is controlled to switch to evaporator, reducing the heat exchange area of ​​the outdoor heat exchanger and reducing the output capacity of the outdoor unit. This avoids the situation of delayed judgment of low load conditions, avoids the state switching lag of the outdoor heat exchanger, avoids the discharge pressure Pd of compressor 11 from further decreasing to below the normal range of compressor discharge pressure, avoids compressor shutdown, and protects the reliability of the unit.

[0186] In some embodiments, reference Figure 13 The controller is configured to: when the first indoor heat exchanger 211 operates as a condenser, the second indoor heat exchanger 212 operates as an evaporator, and both outdoor heat exchangers operate as condensers, if the operating frequency H of the compressor 11 is equal to the minimum frequency Hmin of the compressor 11, the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, the discharge pressure Pd of the compressor 11 is greater than or equal to the preset discharge pressure Pdmin, and the difference between the return air temperature Ti of the indoor unit 2 and the set target temperature Ts is less than the tenth set value, then one of the two outdoor heat exchangers will be switched to evaporator operation. This can reduce the heat exchange area of ​​the outdoor heat exchanger, reduce the output capacity of the outdoor unit, avoid frequent compressor start-stop due to the small difference between the return air temperature Ti of the indoor unit 2 and the set target temperature Ts, and improve the service life of the compressor.

[0187] In some embodiments, the controller is configured to:

[0188] When the first indoor heat exchanger 211 operates as a condenser, the second indoor heat exchanger 212 operates as an evaporator, and the two outdoor heat exchangers operate as evaporators and condensers respectively, if the increase in compressor frequency demanded by the air conditioner ΔH is greater than the twelfth set value, the outdoor heat exchanger operating as an evaporator will be switched to condenser operation. This allows for real-time monitoring of the air conditioner's status and timely adjustment of the outdoor unit's output capacity to meet the needs of the indoor unit when demand increases.

[0189] In some embodiments, reference Figure 16 The controller performs the following steps:

[0190] S30: Air conditioner operates in basic reheat and dehumidification mode;

[0191] S31: The first indoor heat exchanger 211 operates as a condenser, the second indoor heat exchanger 212 operates as an evaporator, and both outdoor heat exchangers operate as condensers.

[0192] S32: Determine whether the operating frequency H of compressor 11 is equal to the minimum frequency Hmin of compressor 11 and whether the speed N of outdoor fan is equal to the minimum speed Nmin of outdoor fan. If not, proceed to step S31. If yes, determine whether the discharge pressure Pd of compressor 11 is less than the preset discharge pressure Pdmin. If yes, proceed to step S33. If no, determine whether the difference between the return air temperature Ti of indoor unit 2 and the set target temperature Ts is less than the tenth set value. If yes, proceed to step S33. If no, proceed to step S31.

[0193] S33: The first indoor heat exchanger 211 operates as a condenser, the second indoor heat exchanger 212 operates as an evaporator, and the two outdoor heat exchangers operate as an evaporator and a condenser, respectively.

[0194] S34: Determine whether the increase in compressor frequency demanded by the air conditioner, ΔH, is greater than the twelfth set value. If yes, proceed to step S31; otherwise, proceed to S33. The tenth set value can be any value between -2℃ and 2℃. The twelfth set value can be any value between 10Hz and 20Hz.

[0195] The basic reheat dehumidification mode operates as follows: the first indoor heat exchanger 211 operates as a condenser, the second indoor heat exchanger 212 operates as an evaporator, and both outdoor heat exchangers operate as condensers. The low-load reheat dehumidification mode operates as follows: the first indoor heat exchanger 211 operates as a condenser, the second indoor heat exchanger 212 operates as an evaporator, and the two outdoor heat exchangers operate as both evaporators and condensers, respectively.

[0196] When the air conditioner is running in the reheat dehumidification mode low load mode, the first commutator 141 and the third commutator 143 are in the second state, and the second commutator 142 and the fourth commutator 144 are in the first state, or the second commutator 142 and the third commutator 143 are in the second state, and the first commutator 141 and the fourth commutator 144 are in the first state.

[0197] When the air conditioner is running in the low-load mode of the reheat dehumidification mode, both the first outdoor fan 171 and the second outdoor fan 172 are working.

[0198] Since low load typically occurs when only one indoor unit 2 is running, taking the operation of one indoor unit 2 as an example, see below. Figure 16 The table shows the refrigerant flow path in the low-load mode of the reheat dehumidification module. Table 3 shows the status of the four reversing devices in different modes.

[0199] Table 3

[0200]

[0201] For ease of explanation, the above description has been provided in conjunction with specific embodiments. However, the above exemplary discussion is not intended to be exhaustive or to limit the embodiments to the specific forms disclosed above. Various modifications and variations can be obtained based on the above teachings. The selection and description of the above embodiments are for the purpose of better explaining the principles and practical applications, thereby enabling those skilled in the art to better utilize the described embodiments and various different variations of embodiments suitable for specific use considerations.

Claims

1. An air conditioner, characterized in that, include: The outdoor unit (1) includes a compressor (11) and two outdoor heat exchangers; The indoor unit (2) has at least one and includes a first indoor heat exchanger (211) and a second indoor heat exchanger (212); A first pressure detection device is used to detect the discharge pressure of the compressor (11); A controller, connected to the first pressure detection device, is configured to: When both the first indoor heat exchanger (211) and the second indoor heat exchanger (212) are operating as evaporators, and both outdoor heat exchangers are operating as condensers, if the operating frequency H of the compressor (11) is equal to the minimum frequency Hmin of the compressor (11), the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, and the discharge pressure Pd of the compressor (11) is less than the preset discharge pressure Pdmin, then one of the two outdoor heat exchangers will be switched to evaporator operation.

2. The air conditioner according to claim 1, characterized in that, The controller is configured to: When both the first indoor heat exchanger (211) and the second indoor heat exchanger (212) are operating as evaporators, and both outdoor heat exchangers are operating as condensers, if the operating frequency H of the compressor (11) is equal to the minimum frequency Hmin of the compressor (11), the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, the exhaust pressure Pd of the compressor (11) is greater than or equal to the preset exhaust pressure Pdmin, and the difference between the return air temperature Ti of the indoor unit (2) and the set target temperature Ts is less than the first set value, then one of the two outdoor heat exchangers will be switched to evaporator operation.

3. The air conditioner according to claim 1 or 2, characterized in that, The indoor unit (2) has an indoor air outlet, and the first indoor heat exchanger (211) is located on the side of the second indoor heat exchanger (212) near the indoor air outlet; The controller is configured to: When both the first indoor heat exchanger (211) and the second indoor heat exchanger (212) are operating as evaporators, and the two outdoor heat exchangers are operating as evaporators and condensers respectively, if the increase in the compressor (11) frequency required by the air conditioner ΔH is less than or equal to the second set value, and the air outlet temperature To of the indoor unit (2) is less than the third preset value, then the first indoor heat exchanger (211) will be switched to condenser operation.

4. The air conditioner according to claim 1 or 2, characterized in that, The controller is configured to: When both the first indoor heat exchanger (211) and the second indoor heat exchanger (212) are operating as evaporators, and the two outdoor heat exchangers are operating as evaporators and condensers respectively, if the increase in compressor (11) frequency required by the air conditioner ΔH is less than or equal to the second set value, the outlet air temperature To of the indoor unit (2) is greater than or equal to the third set value, and the difference between the return air temperature Ti of the indoor unit (2) and the set target temperature Ts is less than the fourth set value, then the first indoor heat exchanger (211) will be switched to condenser operation.

5. The air conditioner according to claim 1, characterized in that, The indoor unit (2) is provided with an indoor air outlet, and the first indoor heat exchanger (211) is located on the side of the second indoor heat exchanger (212) near the indoor air outlet; The controller is configured to: When the first indoor heat exchanger (211) operates as a condenser, the second indoor heat exchanger (212) operates as an evaporator, and both outdoor heat exchangers operate as condensers, if the operating frequency H of the compressor (11) is equal to the minimum frequency Hmin of the compressor (11), the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, and the discharge pressure Pd of the compressor (11) is less than the preset discharge pressure Pdmin, then one of the two outdoor heat exchangers will be switched to operate as an evaporator.

6. The air conditioner according to claim 5, characterized in that, The controller is configured to: When the first indoor heat exchanger (211) operates as a condenser, the second indoor heat exchanger (212) operates as an evaporator, and both outdoor heat exchangers operate as condensers, if the operating frequency H of the compressor (11) is equal to the minimum frequency Hmin of the compressor (11), the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, the discharge pressure Pd of the compressor (11) is greater than or equal to the preset discharge pressure Pdmin, and the difference between the return air temperature Ti of the indoor unit (2) and the set target temperature Ts is less than the tenth set value, then one of the two outdoor heat exchangers will be switched to evaporator operation.

7. The air conditioner according to claim 1, characterized in that, Also includes: The second pressure detection device is used to detect the suction pressure of the compressor (11) and is connected to the controller; The controller is configured to: When both the first indoor heat exchanger (211) and the second indoor heat exchanger (212) are operating as condensers, and both outdoor heat exchangers are operating as evaporators, if the operating frequency H of the compressor (11) is equal to the minimum frequency Hmin of the compressor (11), the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, and the suction pressure Ps of the compressor (11) is greater than the preset suction pressure Psmax, then one of the two outdoor heat exchangers will be switched to condenser operation.

8. The air conditioner according to claim 7, characterized in that, The controller is configured to: When both the first indoor heat exchanger (211) and the second indoor heat exchanger (212) are operating as condensers, and both outdoor heat exchangers are operating as evaporators, if the operating frequency H of the compressor (11) is equal to the minimum frequency Hmin of the compressor (11), the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, the suction pressure Ps of the compressor (11) is less than or equal to the preset discharge pressure Psmax, and the difference between the set target temperature Ts and the return air temperature Ti of the indoor unit (2) is less than the sixth set value, then one of the two outdoor heat exchangers will be switched to condenser operation.

9. The air conditioner according to claim 7 or 8, characterized in that, The controller is configured to: When both the first indoor heat exchanger (211) and the second indoor heat exchanger (212) are operating as condensers, and the two outdoor heat exchangers are operating as evaporators and condensers respectively, if the increase in the compressor (11) frequency required by the air conditioner ΔH is less than or equal to the seventh preset value and the air outlet temperature To of the indoor unit (2) is greater than the eighth preset value, then the first indoor heat exchanger (211) switches to evaporator operation; And / or, when the first indoor heat exchanger (211) and the second indoor heat exchanger (212) are both operating as condensers, and the two outdoor heat exchangers are operating as evaporators and condensers respectively, if the increase in compressor (11) frequency required by the air conditioner ΔH is less than or equal to the seventh set value, the outlet air temperature To of the indoor unit (2) is less than or equal to the eighth preset value, and the difference between the set target temperature Ts and the return air temperature Ti of the indoor unit (2) is less than the ninth set value, then the first indoor heat exchanger (211) switches to evaporator operation.

10. An air conditioner, characterized in that, include: The outdoor unit (1) includes a compressor (11) and two outdoor heat exchangers; The indoor unit (2) has at least one and includes a first indoor heat exchanger (211) and a second indoor heat exchanger (212); The second pressure detection device is used to detect the suction pressure of the compressor (11); A controller, connected to the second pressure detection device, is configured to: When both the first indoor heat exchanger (211) and the second indoor heat exchanger (212) are operating as condensers, and both outdoor heat exchangers are operating as evaporators, if the operating frequency H of the compressor (11) is equal to the minimum frequency Hmin of the compressor (11), the speed N of the outdoor fan is equal to the minimum speed Nmin of the outdoor fan, and the suction pressure Ps of the compressor (11) is greater than the preset suction pressure Psmax, then one of the two outdoor heat exchangers will be switched to condenser operation.

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