Air conditioner

Abstract

The present application provides an air conditioner. Comprising: a housing, an air flow path for outdoor air to flow into the indoor is formed inside; a first heat exchanger, configured on the air flow path, the refrigerant flows in the first heat exchanger; a second heat exchanger, configured on the air flow path downstream of the first heat exchanger, the refrigerant selectively flows in the second heat exchanger; a liquid pipe, connected with the first heat exchanger and the second heat exchanger respectively, the liquid refrigerant flows in the liquid pipe; a high-pressure gas pipe, connected with the first heat exchanger and the second heat exchanger respectively, the gaseous refrigerant flows in the high-pressure gas pipe; a low-pressure gas pipe, the gaseous refrigerant discharged from the first heat exchanger and the second heat exchanger flows in the low-pressure gas pipe; a high-pressure gas pipe valve, provided in the high-pressure gas pipe; a low-pressure gas pipe valve, provided in the low-pressure gas pipe; an expansion valve, provided in the liquid pipe; and a control unit, based on the temperature of the refrigerant flowing in the first heat exchanger, controls the opening degree of the low-pressure gas pipe valve.

Description

Technical Field

[0001] This invention relates to air conditioners. Background Technology

[0002] The ventilation system can regulate the temperature of the air supplied to the room by heat exchange between indoor air exhausted to the outside and outdoor air supplied to the room, or by adding a heater to heat the air flowing into the room.

[0003] Therefore, in cooling mode, it can cool or dehumidify the air flowing in from the outside and supply the cooled and dehumidified air to the indoor space.

[0004] In this regard, Korean Patent No. 10-1782839, which is existing literature, discloses a structure that uses a heater to reheat the air flowing into the room.

[0005] However, in the case of the existing literature, excessive power consumption is caused by using an additional power-consuming heater to regulate the temperature of the flowing air, resulting in a decrease in energy efficiency.

[0006] In addition, when external gas is introduced into the air conditioning system for dehumidification, cooling, or heating, the compressor frequency can be increased to achieve full dehumidification performance.

[0007] However, under these circumstances, the surface temperature of the dehumidification coil is low, causing the dehumidification coil to freeze and crack, resulting in reduced airflow and decreased heat exchange performance.

[0008] In order to solve this freezing and cracking problem, in recent years, research has been conducted on methods such as making high-temperature refrigerant flow in the dehumidification coil, or making the refrigerant flowing into the dehumidification coil exchange heat with the high-temperature refrigerant discharged from the condenser, or making the air passing through the dehumidification coil exchange heat with the preheating coil in which hot water flows.

[0009] However, with existing anti-freezing technologies, the complexity of air conditioning systems leads to increased product costs and maintenance expenses. Furthermore, the additional operation required for de-icing makes it difficult to ensure adequate dehumidification performance and reduces continuous operating time.

[0010] Patent Document 1: Korean Patent No. 10-1782839 (Grant Date: September 22, 2017). Summary of the Invention

[0011] The present invention is proposed to solve the above-mentioned problems, and its purpose is to provide an air conditioner that can prevent the dehumidification coil from freezing and cracking.

[0012] Another objective of this invention is to provide an air conditioner that can easily regulate the temperature and humidity of the air supplied to the room through a plurality of heat exchangers.

[0013] The present invention also aims to provide an air conditioner that, even without performing additional operations to prevent the dehumidification coil from freezing and cracking, helps to ensure sufficient dehumidification performance and increase continuous operating time.

[0014] Another objective of this invention is to provide an air conditioner that can prevent the dehumidification coil from freezing and cracking by controlling the indoor evaporation pressure at a higher level than the outdoor evaporation pressure.

[0015] Another objective of this invention is to provide an air conditioner that can control the pressure of the dehumidification coil and the surface temperature by adjusting the opening of the expansion valve.

[0016] Another objective of this invention is to provide an air conditioner that adjusts the opening of the expansion valve based on the temperature of the refrigerant flowing in the dehumidification coil, thereby preventing frost formation on the dehumidification coil.

[0017] An air conditioner according to an embodiment of the present invention for achieving the above-mentioned objectives includes: a housing having an airflow path formed inside for outdoor air to flow into the room; a first heat exchanger disposed on the airflow path, wherein refrigerant flows in the first heat exchanger to exchange heat between the flowing air and the refrigerant; a second heat exchanger disposed downstream of the first heat exchanger on the airflow path, wherein refrigerant selectively flows in the second heat exchanger to exchange heat between the flowing air and the refrigerant; a liquid pipe connected to the first heat exchanger and the second heat exchanger respectively, wherein liquid refrigerant flows; a high-pressure gas pipe connected to the first heat exchanger and the second heat exchanger respectively, wherein gaseous refrigerant flows in the high-pressure gas pipe; a low-pressure gas pipe through which gaseous refrigerant discharged from the first heat exchanger and the second heat exchanger flows; a high-pressure gas pipe valve disposed on the high-pressure gas pipe; a low-pressure gas pipe valve disposed on the low-pressure gas pipe; an expansion valve disposed on the liquid pipe; and a control unit that controls the opening degree of the low-pressure gas pipe valve based on the temperature of the refrigerant flowing in the first heat exchanger.

[0018] Based on this configuration, the opening of the low-pressure gas pipe valve is controlled according to the refrigerant temperature of the dehumidification coil, thereby making the indoor evaporation pressure higher than the outdoor evaporation pressure, which can prevent the heat exchanger from freezing and cracking.

[0019] The control unit can control the opening degree of the low-pressure gas pipe valve based on the refrigerant temperature on the inlet side or the refrigerant temperature on the outlet side of the first heat exchanger.

[0020] The control unit can determine whether the refrigerant temperature at the inlet side of the first heat exchanger is less than a set value. If the refrigerant temperature at the inlet side of the first heat exchanger is less than the set value, the control unit can reduce the opening of the low-pressure gas pipe valve.

[0021] When the refrigerant temperature at the inlet side of the first heat exchanger is above a set value, the control unit can increase or maintain the opening of the low-pressure gas pipe valve.

[0022] The control unit can determine whether the refrigerant temperature at the outlet side of the first heat exchanger is less than a set value. If the refrigerant temperature at the outlet side of the first heat exchanger is less than the set value, the control unit can reduce the opening of the low-pressure gas pipe valve.

[0023] When the refrigerant temperature at the outlet side of the first heat exchanger is above a set value, the control unit can increase or maintain the opening of the low-pressure gas pipe valve.

[0024] The control unit can determine whether the conditions for entering the freeze-crack prevention mode for the first heat exchanger are met. If the conditions for entering the freeze-crack prevention mode are met, the control unit can control the opening degree of the low-pressure gas pipe valve based on the temperature of the refrigerant flowing in the first heat exchanger.

[0025] The conditions for entering the freeze-crack prevention mode may include the refrigerant temperature on the inlet side of the first heat exchanger being less than a first set value or the refrigerant temperature on the outlet side of the first heat exchanger being less than a first set value.

[0026] When the conditions for entering the freeze-crack prevention mode are met, the control unit can determine whether the refrigerant temperature at the inlet side of the first heat exchanger is less than a second set value that is smaller than the first set value. If the refrigerant temperature at the inlet side of the first heat exchanger is less than the second set value, the control unit can reduce the opening of the low-pressure gas pipe valve.

[0027] When the refrigerant temperature at the inlet side of the first heat exchanger is above the second set value, the control unit may increase or maintain the opening of the low-pressure gas pipe valve.

[0028] When the conditions for entering the freeze-crack prevention mode are met, the control unit can determine whether the refrigerant temperature on the outlet side of the first heat exchanger is less than a second set value that is smaller than the first set value. If the refrigerant temperature on the outlet side of the first heat exchanger is less than the second set value, the control unit can reduce the opening of the low-pressure gas pipe valve.

[0029] When the refrigerant temperature at the outlet side of the first heat exchanger is above the second set value, the control unit may increase or maintain the opening of the low-pressure gas pipe valve.

[0030] The conditions for entering the freeze-crack prevention mode may include a situation where the temperature of the air passing through the first heat exchanger is less than a first set value.

[0031] If the conditions for entering the freeze-crack prevention mode are not met, the control unit can determine whether the difference between the refrigerant temperature on the inlet side and the refrigerant temperature on the outlet side of the first heat exchanger is less than a reference value. If the difference between the refrigerant temperature on the inlet side and the refrigerant temperature on the outlet side of the first heat exchanger is less than the reference value, the control unit can increase the opening of the expansion valve.

[0032] When the difference between the refrigerant temperature on the inlet side and the refrigerant temperature on the outlet side of the first heat exchanger is above a reference value, the control unit can reduce the opening degree of the expansion valve.

[0033] In the cooling mode or cooling-dehumidification mode of the air conditioner, the control unit can control the opening degree of the low-pressure gas pipe valve.

[0034] In the cooling mode, the first heat exchanger functions as an evaporator, and there is no refrigerant flow in the second heat exchanger.

[0035] In the cooling and dehumidification mode, the first heat exchanger functions as an evaporator, and the second heat exchanger functions as a condenser.

[0036] The low-pressure gas pipe valve may include an electronic expansion valve (EEV) that regulates the pressure of the refrigerant by adjusting its opening degree, and the flow coefficient of the low-pressure gas pipe valve may be greater than the flow coefficient of the expansion valve.

[0037] The air conditioner also includes an outdoor unit, which has a compressor for compressing refrigerant, an outdoor heat exchanger for exchanging heat between the refrigerant and outdoor air, and an outdoor expansion valve for expanding the refrigerant. The flow coefficient of the low-pressure gas pipe valve can be greater than the flow coefficient of the outdoor expansion valve.

[0038] The air conditioner according to the embodiment of the present invention constructed as described above has the following effects.

[0039] First, it can prevent icing from occurring in the dehumidification coil when external gas is introduced and refrigeration or dehumidification is performed.

[0040] Specifically, the opening of the low-pressure gas pipe valve is controlled based on the temperature of the refrigerant flowing in the dehumidification coil, thereby making the indoor evaporation pressure higher than the outdoor evaporation pressure, thus preventing the dehumidification coil from freezing and cracking in advance.

[0041] Secondly, since the pressure of the dehumidification coil and the surface temperature are controlled by adjusting the opening of the valve, there is no need to perform additional operations to prevent freezing and cracking, which has the advantage of helping to increase the continuous operating time of the air conditioner.

[0042] Third, because the opening of the electronic expansion valve is precisely controlled by the refrigerant temperature of the dehumidification coil, it not only has the advantage of preventing the dehumidification coil from freezing and cracking, but also has the advantage of ensuring sufficient cooling and dehumidification performance.

[0043] Fourth, since the dehumidification coil can be prevented from freezing and cracking through a simple structure and algorithm without the need for additional parts, it has the advantages of reduced product cost and easier maintenance. Attached Figure Description

[0044] Figure 1 This is a diagram illustrating the configuration of an outdoor unit and a plurality of indoor units in a building according to an embodiment of the present invention.

[0045] Figure 2 This is a diagram illustrating the internal structure of the indoor unit in an embodiment of the present invention.

[0046] Figure 3 This is a side view used to illustrate the internal structure of the indoor unit in an embodiment of the present invention.

[0047] Figure 4 This is a piping diagram illustrating the configuration of the indoor unit according to an embodiment of the present invention.

[0048] Figure 5 This is a piping diagram illustrating the refrigerant flow in the heating mode of the indoor unit in an embodiment of the present invention.

[0049] Figure 6 This is a flowchart illustrating a control method for an air conditioner in the heating mode of the indoor unit in an embodiment of the present invention.

[0050] Figure 7 This is a piping diagram illustrating the refrigerant flow in the cooling mode of the indoor unit in an embodiment of the present invention.

[0051] Figure 8 This is a flowchart illustrating a control method for an air conditioner in the cooling mode of the indoor unit in an embodiment of the present invention.

[0052] Figure 9 and Figure 10This is a piping diagram illustrating the refrigerant flow in the cooling and dehumidification mode of the indoor unit in an embodiment of the present invention.

[0053] Figure 11 and Figure 12 This is a flowchart illustrating the control method of an air conditioner in the cooling and dehumidification mode of the indoor unit in an embodiment of the present invention.

[0054] Figure 13 This is a piping diagram illustrating the refrigerant flow in the defrost mode of an embodiment of the present invention.

[0055] Figure 14 This is a flowchart illustrating the control method of an air conditioner in defrost mode according to an embodiment of the present invention. Detailed Implementation

[0056] Hereinafter, some embodiments of the present invention will be described in detail with reference to the exemplary accompanying drawings. It should be noted that when assigning reference numerals to the structural elements of the various drawings, the same symbols are used as much as possible for the same structural elements, even though they are labeled in different drawings. Furthermore, in the process of describing the embodiments of the present invention, detailed descriptions of related well-known structures or functions are omitted if they are deemed to hinder understanding of the embodiments of the present invention.

[0057] Furthermore, when describing the structural elements of embodiments of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are used only to distinguish the structural elements from other structural elements and do not limit the nature, order, or sequence of the corresponding structural elements. When a structural element is described as "connected," "combined," or "attached" to other structural elements, it should be understood that the structural element can directly connect to or link to the other structural elements, and that structural elements can also be "connected," "combined," or "attached" to each other to another structural element.

[0058] The present invention will now be described with reference to the accompanying drawings illustrating the air conditioner, through embodiments thereof.

[0059] Figure 1 This is a diagram illustrating the configuration of an outdoor unit and a plurality of indoor units in a building according to an embodiment of the present invention. Figure 2 This is a diagram illustrating the internal structure of the indoor unit in an embodiment of the present invention. Figure 3 This is a side view used to illustrate the internal structure of the indoor unit in an embodiment of the present invention. Figure 4 This is a piping diagram illustrating the configuration of the indoor unit according to an embodiment of the present invention.

[0060] First, refer to Figure 1The air conditioner of the present invention may include: an outdoor unit 1 disposed in the external space of a building or the like; and indoor units 10a, 10b, 10c, and 10d disposed in the indoor space of a building or the like. The air conditioner of the present invention may include at least one outdoor unit 1 and a plurality of indoor units 10a, 10b, 10c, and 10d.

[0061] Outdoor unit 1 and indoor units 10a, 10b, 10c, and 10d can be connected using a plurality of refrigerant pipes. Outdoor unit 1 of this invention can be connected via three refrigerant pipes 30, 40, and 50 (see reference). Figure 4 It is connected to the indoor unit. The indoor unit 10 of the present invention can be a ventilation device that allows external air to flow in, regulates the temperature through a heat exchanger, and then supplies it to the room.

[0062] Below, refer to Figures 2 to 4 The internal structure and flow path of indoor unit 10 are explained by examining the configuration of one of a plurality of indoor units 10. Therefore, referring to... Figures 2 to 4 The description of one indoor unit 10 can also be applied to multiple other indoor units.

[0063] Reference Figure 2 and Figure 3 The indoor unit 10 of the present invention includes: a housing 12 forming the exterior and having an internal space for airflow; a fan 14 disposed inside the housing 12 to create airflow; a first heat exchanger 16 disposed in the internal space of the housing 12 for heat exchange between refrigerant and air; a second heat exchanger 18 disposed in the internal space of the housing 12 for heat exchange between refrigerant and air; and a refrigerant distributor 20 connected to a plurality of refrigerant pipes 30, 40, 50 to supply refrigerant flowing from the outdoor unit 1 to the first heat exchanger 16 or the second heat exchanger 18.

[0064] The first heat exchanger 16 can be referred to as the "main coil" or the "dehumidification coil".

[0065] The second heat exchanger 18 may be referred to as a "sub coil" or a "reheat coil".

[0066] An intake port 12a and an exhaust port 12b are formed on one side of the housing 12. Supply flow paths 12c and 12d are formed inside the housing 12 for air to flow in from the interior. The supply flow paths may include: an exhaust chamber 12d for discharging air from inside the housing 12 to the outside; and an intake chamber 12c for allowing outside air to flow into the housing 12.

[0067] Additionally, a partition wall 13 is formed on the inner side of the housing 12 to separate the intake chamber 12c and the exhaust chamber 12d. A communication hole is formed in the partition wall 13 to allow air from the intake chamber 12c to flow into the exhaust chamber 12d.

[0068] A first heat exchanger 16 and a second heat exchanger 18 are configured on the supply flow paths 12c and 12d.

[0069] In the supply flow paths 12c and 12d, the second heat exchanger 18 is disposed downstream of the first heat exchanger 16. That is, based on the air flow direction, the first heat exchanger 16 is disposed first, and then the second heat exchanger 18 is disposed.

[0070] Specifically, the first heat exchanger 16 and the second heat exchanger 18 are disposed in the suction chamber 12c. The first heat exchanger 16 and the second heat exchanger 18 are disposed between the partition wall 13 and the suction port 12a.

[0071] The first heat exchanger 16 is positioned adjacent to the intake port 12a, and the second heat exchanger 18 is positioned adjacent to the partition wall 13. Therefore, air flowing into the intake chamber 12c through the intake port 12a can flow to the exhaust chamber 12d via the first heat exchanger 16 and the second heat exchanger 18.

[0072] The flow rate of refrigerant flowing through the first heat exchanger 16 can be greater than the flow rate of refrigerant flowing through the second heat exchanger 18. That is, the flow path area of ​​the first heat exchanger 16 is greater than the flow path area of ​​the second heat exchanger 18. Therefore, the temperature change of the air in the first heat exchanger 16 can be greater than the temperature change of the air in the second heat exchanger 18.

[0073] In some embodiments, since the cooling performance of the first heat exchanger 16 is greater than the heating performance of the second heat exchanger 18, air can be cooled by passing through the first heat exchanger 16 and dehumidified by passing through the second heat exchanger 18, and the cooled and dehumidified air can flow into the room.

[0074] The exhaust chamber 12d is provided with the air supply fan 14 and the fan motor 15 that rotates the air supply fan 14. The exhaust chamber 12d may be provided with a fan support 15a that supports the air supply fan 14 and the fan motor 15.

[0075] The air supply fan 14 can be a plug-in fan, which has an intake port formed along the direction of the rotation axis and an exhaust port formed in the direction perpendicular to the rotation axis.

[0076] A space for configuring a refrigerant distributor 20 can be formed inside the housing 12. The refrigerant distributor 20 is connected to the first heat exchanger 16 and the second heat exchanger 18. The refrigerant distributor 20 can be configured on one side of the suction chamber 12c. The refrigerant distributor 20 is configured inside the housing 12 and connects the outdoor unit 1 to the first heat exchanger 16 and the second heat exchanger 18.

[0077] The refrigerant distributor 20 includes a plurality of refrigerant pipes and a plurality of valves. In this embodiment, the refrigerant distributor 20 is described as being built into the indoor unit 10.

[0078] Reference Figure 4 The indoor unit 10 includes a plurality of refrigerant pipes 30, 40, 50 and a plurality of valves.

[0079] The plurality of refrigerant pipes 30, 40, and 50 include: a liquid pipe 30, connecting the outdoor unit 1 to the first heat exchanger 16 and the second heat exchanger 18, through which liquid refrigerant flows; a high-pressure gas pipe 40, connecting the outdoor unit 1 to the first heat exchanger 16 and the second heat exchanger 18, through which gaseous refrigerant flows; and a low-pressure gas pipe 50, connecting the outdoor unit 1 to the first heat exchanger 16.

[0080] The plurality of valves may include: high-pressure gas pipe valves 44 and 48, disposed on the high-pressure gas pipe 40, for supplying refrigerant flowing in the high-pressure gas pipe 40 to the first heat exchanger 16 or the second heat exchanger 18; low-pressure gas pipe valve 54, disposed on the low-pressure gas pipe 50, for opening and closing the low-pressure gas pipe 50; and expansion valves 34 and 38, disposed on the liquid pipe 30, for opening and closing the liquid pipe 30.

[0081] The liquid pipe 30 includes: a first liquid pipe 32 connected to the first heat exchanger 16; and a second liquid pipe 36 branching from the first liquid pipe 32 at a branch point 35 and connected to the second heat exchanger 18. The branch point 35 may be formed at a location between the supercooler 70 and the first expansion valve 34, described later.

[0082] A first expansion valve 34 is provided in the first liquid pipe 32 to expand the refrigerant flowing to the first heat exchanger 16, and a second expansion valve 38 is provided in the second liquid pipe 36 to expand the refrigerant flowing to the second heat exchanger 18.

[0083] An overcooler 70 is provided in the liquid pipe 30, which overcools the refrigerant flowing in the liquid pipe 30 by causing a portion of the refrigerant flowing in the liquid pipe 30 to expand and exchange heat.

[0084] The inlet side of the supercooler 70 can be connected to the liquid pipe 30, and the outlet side of the supercooler 70 can be connected to the low-pressure gas pipe 50.

[0085] A portion of the refrigerant flowing in the liquid line 30 flows through a branch pipe 74 that branches off from a portion of the liquid line 30. The branch pipe 74 connects the liquid line 30 and the subcooler 70. A subcooling expansion valve 76 for depressurizing the refrigerant may be configured in the branch pipe 74.

[0086] The refrigerant flowing along the branch pipe 74 can pass through the supercooler 70 after passing through the supercooled expansion valve 76. The refrigerant that has passed through the supercooler 70 can flow into the low-pressure gas pipe 50 and merge with the refrigerant in the low-pressure gas pipe 50.

[0087] The high-pressure air pipe 40 includes: a first high-pressure air pipe 42 connected to the first heat exchanger 16; and a second high-pressure air pipe 46 branching off from a portion of the first high-pressure air pipe 42 and connected to the second heat exchanger 18.

[0088] The first high-pressure air pipe 42 is provided with a first high-pressure air pipe valve 44 for opening and closing the first high-pressure air pipe 42, and the second high-pressure air pipe 44 is provided with a second high-pressure air pipe valve 48 for opening and closing the second high-pressure air pipe 46.

[0089] The first high-pressure gas line valve 44 may include an electronic expansion valve (EEV) capable of regulating the refrigerant flow rate by adjusting its opening degree. The electronic expansion valve can reduce the pressure of the refrigerant passing through the first high-pressure gas line valve 44 by adjusting its opening degree.

[0090] As an example, if the electronic expansion valve is fully open, the refrigerant can pass through without pressure reduction; if the opening of the electronic expansion valve is reduced, the refrigerant pressure can be reduced. The degree of refrigerant pressure reduction can increase as the opening of the electronic expansion valve decreases.

[0091] The low-pressure gas pipe 50 is connected to the first heat exchanger 16. The low-pressure gas pipe 50 can also be connected to the first high-pressure gas pipe 42. A low-pressure gas pipe valve 54 is provided on the low-pressure gas pipe 50 to open and close the low-pressure gas pipe 50.

[0092] The low-pressure gas valve 54 may include an electronic expansion valve (EEV) capable of regulating the flow rate of refrigerant by adjusting its opening degree.

[0093] In this embodiment, the flow coefficients of the first high-pressure gas valve 44 and the low-pressure gas valve 54 are greater than the flow coefficients of the second high-pressure gas valve 48, the first expansion valve 34, and the second expansion valve 38, so as to control the indoor evaporation pressure to be greater than the outdoor evaporation pressure. That is, the icing of the first heat exchanger 16 can be prevented by making the evaporation force of the first heat exchanger 16 relatively high.

[0094] The indoor unit 10 may also include a humidity sensor HU and a plurality of temperature sensors T1 to T6.

[0095] The humidity sensor HU can be understood as a sensor used to sense the humidity of outdoor air. The sensed humidity can be provided to the control unit of the indoor unit 10 or the outdoor unit 1. The humidity sensed by the humidity sensor HU can be defined as the "current humidity value".

[0096] This can be understood as the plurality of temperature sensors T1 to T6 being sensors used to sense the temperature of the air or refrigerant. The sensed temperature can be provided to the control unit of the indoor unit 10 or the outdoor unit 1.

[0097] Specifically, the plurality of temperature sensors may include a first temperature sensor T1 to a sixth temperature sensor T6.

[0098] The first temperature sensor T1 can sense the temperature of the outdoor air. The first temperature sensor T1 can sense the temperature of the outdoor air before it passes through the first heat exchanger 16.

[0099] The temperature sensed by the first temperature sensor T1 can be defined as the "first temperature value" or the "heat exchanger air inlet temperature".

[0100] The second temperature sensor T2 can sense the temperature of the outdoor air after it has passed through the first heat exchanger 16.

[0101] The temperature sensed by the second temperature sensor T2 can be defined as the "second temperature value" or the "heat exchanger air outlet temperature".

[0102] The first temperature sensor T1 and the second temperature sensor T2 can be disposed around the first heat exchanger 16.

[0103] The third temperature sensor T3 can sense the temperature of the outdoor air after it has passed through the first heat exchanger 16 and the second heat exchanger 18. The third temperature sensor T3 can also sense the temperature of the air discharged from the air outlet fan 14 of the indoor unit 10. The third temperature sensor T3 can be located on the air outlet side of the air outlet fan 14.

[0104] The temperature sensed by the third temperature sensor T3 can be defined as the "third temperature value" or "air exhaust temperature".

[0105] The fourth temperature sensor T4 can sense the refrigerant temperature on the inlet side of the first heat exchanger 16. As an example, the fourth temperature sensor T4 can be located on the piping inlet side of the first heat exchanger 16.

[0106] The temperature sensed by the fourth temperature sensor T4 can be defined as the "fourth temperature value" or the "refrigerant temperature at the heat exchanger inlet".

[0107] The fifth temperature sensor T5 can sense the refrigerant temperature on the outlet side of the first heat exchanger 16. As an example, the fifth temperature sensor T5 can be located on the piping outlet side of the first heat exchanger 16.

[0108] The temperature sensed by the fifth temperature sensor T5 can be defined as the "fifth temperature value" or the "refrigerant temperature at the heat exchanger outlet".

[0109] The sixth temperature sensor T6 can sense the refrigerant temperature on the outlet side of the second heat exchanger 18. For example, the sixth temperature sensor T6 can be located on the outlet side of the second heat exchanger 18. The temperature sensed by the sixth temperature sensor T6 can be defined as the "sixth temperature value".

[0110] As mentioned above, in the air conditioner of the present invention, an outdoor unit 1 is connected to a plurality of indoor units 10. The air conditioner of the present invention can operate in a heating mode M1, in which only a portion of the plurality of indoor units 10 is used for heating; a cooling mode M2, in which only a portion of the plurality of indoor units 10 is used for cooling; a cooling and dehumidifying mode M3, in which a portion of the plurality of indoor units 10 is used for cooling and another portion is used for heating; and a defrosting mode M4, used for defrosting the outdoor heat exchanger while operating in heating mode.

[0111] Figure 5This is a piping diagram illustrating the refrigerant flow in the heating mode of the indoor unit according to an embodiment of the present invention. Hereinafter, referring to... Figure 5 The heating mode M1 is explained.

[0112] In heating mode M1, only the liquid pipe 30 and the high-pressure gas pipe 40 can be used, and the refrigerant will not flow into the low-pressure gas pipe 50. In heating mode M1, the refrigerant flows from the outdoor unit 1 to the indoor unit 10 through the high-pressure gas pipe 40, and the refrigerant in the indoor unit 10 flows to the outdoor unit 1 through the liquid pipe 30.

[0113] At this time, the first high-pressure gas pipe valve 44, the first expansion valve 34, and the supercooled expansion valve 76 are opened, while the second high-pressure gas pipe valve 48, the second expansion valve 38, and the low-pressure gas pipe valve 54 are closed.

[0114] The outdoor heat exchanger of the outdoor unit 1 functions as an evaporator, and the first heat exchanger 16 functions as a condenser. Furthermore, the refrigerant does not flow to the second heat exchanger 18.

[0115] If the air conditioner is operating in heating mode M1, the high-temperature, high-pressure refrigerant compressed by the compressor in the outdoor unit 1 flows into the indoor unit 10 through the first high-pressure gas pipe 42. Furthermore, the refrigerant in the first high-pressure gas pipe 42 flows into the first heat exchanger 16 through the first high-pressure gas pipe valve 44 and is condensed. At this time, the first high-pressure gas pipe valve 44 can be in a fully open state.

[0116] The condensed refrigerant discharged from the first heat exchanger 16 flows into the subcooler 70 after passing through the first liquid pipe 32 and the first expansion valve 34. At this time, the first expansion valve 34 may be in a partially open state.

[0117] A portion of the refrigerant flowing into the supercooler 70 passes through the supercooling expansion valve 76, supercooling the refrigerant flowing in the liquid line 30, while the remaining portion flows into the outdoor unit 1 through the first liquid line 32. The refrigerant flowing into the outdoor unit 1 is evaporated in the outdoor heat exchanger and then recovered to the compressor.

[0118] Figure 6 This is a flowchart illustrating a control method for an air conditioner in the heating mode of the indoor unit in an embodiment of the present invention.

[0119] Reference Figure 6 The air conditioner uses temperature and humidity information to determine the operating mode as heating mode.

[0120] Temperature information may include the current outdoor air temperature value sensed by the first temperature sensor T1 and the set temperature value input by the user.

[0121] Humidity information may include the current humidity value of the outdoor air sensed by the humidity detection sensor HU and a set humidity value input by the user.

[0122] For example, if the set temperature value input by the user is higher than the current outdoor air temperature, the air conditioner can operate in heating mode M1 (S10).

[0123] If operating in heating mode M1, the first high-pressure gas valve 44 is fully open, and the low-pressure gas valve 54, the second expansion valve 38, and the second high-pressure gas valve 48 are closed. Thus, the first heat exchanger 16 functions as a condenser, and the outdoor heat exchanger of the outdoor unit 1 functions as an evaporator. The second heat exchanger 18 is not used (S11).

[0124] The air conditioner can achieve a suitable level of heating by controlling the opening of the first expansion valve 34. The air conditioner can determine whether the current hot water production level of the indoor unit is at the target level (set level). To do this, the air conditioner determines whether the difference between the condensing temperature and the fifth temperature value is less than a reference value.

[0125] Here, the condensing temperature represents the outdoor condensing temperature sensed by the sensor installed on the outdoor unit 1, the fifth temperature value represents the temperature sensed by the fifth temperature detection sensor T5, and the reference value represents the preset temperature value (S12).

[0126] If the difference between the condensing temperature and the fifth temperature value is less than the target value, the air conditioner determines that the current indoor unit's hot water production level has not reached the target level, and increases the opening of the first expansion valve 34.

[0127] If the opening of the first expansion valve 34 is increased, the flow rate of refrigerant through the first expansion valve 34 will further increase, so the current hot water production level of the indoor unit can be increased in a manner close to the target level (S13).

[0128] Conversely, if the difference between the condensing temperature and the fifth temperature value is greater than the reference value, the air conditioner determines that the current indoor unit's hot water production level exceeds the target level, and reduces the opening of the first expansion valve 34.

[0129] If the opening of the first expansion valve 34 decreases, the flow rate of refrigerant through the first expansion valve 34 decreases relatively, so the current hot water production level of the indoor unit can be reduced in a manner close to the target level (S14).

[0130] On the other hand, the air conditioner determines whether an operation end command has been input through the input unit, and stops the operation of the compressor and the air supply fan 14 if an operation end command has been input, and enters S12 (S15, S16) again if no operation end command has been input.

[0131] Figure 7 This is a piping diagram illustrating the refrigerant flow in the cooling mode of the indoor unit according to an embodiment of the present invention. Hereinafter, referring to... Figure 7 The cooling mode M2 ​​is explained.

[0132] In cooling mode M2, only the liquid pipe 30 and the low-pressure gas pipe 50 are used, and the refrigerant does not flow into the high-pressure gas pipe 40. In cooling mode M2, the refrigerant flows from the outdoor unit 1 to the indoor unit 10 through the liquid pipe 30, and the refrigerant in the indoor unit 10 flows to the outdoor unit 1 through the low-pressure gas pipe 50.

[0133] At this time, the low-pressure gas pipe valve 54, the first expansion valve 34, and the supercooled expansion valve 76 are opened, while the first high-pressure gas pipe valve 44, the second high-pressure gas pipe valve 48, and the second expansion valve 38 are closed.

[0134] The outdoor heat exchanger of the outdoor unit 1 functions as a condenser, and the first heat exchanger 16 functions as an evaporator. Furthermore, refrigerant does not flow to the second heat exchanger 18.

[0135] If the air conditioner is operating in cooling mode M2, the high-temperature, high-pressure refrigerant compressed by the compressor in the outdoor unit 1 is condensed in the outdoor heat exchanger of the outdoor unit 1, and then flows into the indoor unit 10 through the liquid pipe 30. Furthermore, a portion of the refrigerant in the liquid pipe 30 flows into the subcooled expansion valve 76 through the branch pipe 74, while the remaining portion flows into the first expansion valve 34 through the first liquid pipe 32.

[0136] The refrigerant that has passed through the first expansion valve 34 is depressurized and flows into the first heat exchanger 16 where it is evaporated. The refrigerant discharged from the first heat exchanger 16 passes through the low-pressure gas pipe 50 and the low-pressure gas pipe valve 54. At this time, the low-pressure gas pipe valve 54 can be in a fully open state or a partially open state.

[0137] The refrigerant passing through the low-pressure gas pipe valve 54 flows along the low-pressure gas pipe 50 into the compressor of the outdoor unit 1.

[0138] Figure 8This is a flowchart illustrating a control method for an air conditioner in the cooling mode of the indoor unit in an embodiment of the present invention.

[0139] Reference Figure 8 The air conditioner uses temperature and humidity information to determine the operating mode as cooling mode.

[0140] Temperature information may include the current outdoor air temperature value sensed by the first temperature sensor T1 and the set temperature value input by the user.

[0141] Humidity information may include the current humidity value of the outdoor air sensed by the humidity detection sensor HU and a set humidity value input by the user.

[0142] For example, if the set temperature value input by the user is lower than the current outdoor air temperature value, and the set humidity value input by the user is higher than the current outdoor air humidity value, the air conditioner can operate in cooling mode M2 ​​(S20).

[0143] If operating in cooling mode M2, the first high-pressure gas valve 44 is closed, the low-pressure gas valve 54 is opened, and the second expansion valve 38 and the second high-pressure gas valve 48 are closed. Thus, the outdoor heat exchanger of the outdoor unit 1 functions as a condenser, and the first heat exchanger 16 functions as an evaporator. The second heat exchanger 18 is not used (S21).

[0144] The air conditioner can prevent the indoor heat exchanger (dehumidifying coil) from freezing by controlling the opening of the low-pressure gas pipe valve 54. To this end, the air conditioner determines whether the conditions for entering the freeze prevention mode of the indoor heat exchanger have been met.

[0145] Specifically, the conditions for entering the freeze prevention mode may include a situation where the refrigerant temperature on the inlet side of the first heat exchanger 16 is less than a first set value, or a situation where the refrigerant temperature on the outlet side of the first heat exchanger 16 is less than the first set value, or a situation where the temperature of the air passing through the first heat exchanger 16 is less than the first set value. Here, the first set value may be a preset temperature, which can be set by the user.

[0146] In other words, if the first temperature value, or the second temperature value, or the fourth temperature value, or the fifth temperature value is less than the first set value, the air conditioner can enter the freeze prevention mode (S22).

[0147] If the freeze prevention mode is entered, the air conditioner will determine whether the current value is greater than the second set value.

[0148] Here, the current value can be the temperature value sensed by the fourth temperature sensor T4 or the temperature value sensed by the fifth temperature sensor T5. Alternatively, the current value can be the average of the fourth and fifth temperature values.

[0149] The second setting value represents a preset temperature value. The second setting value can be a temperature lower than the first setting value (S23).

[0150] If the current value is greater than the second set value, the air conditioner determines that the possibility of icing in the indoor heat exchanger is small, thereby maintaining or increasing the opening of the low-pressure gas pipe valve 54.

[0151] If the opening degree of the low-pressure gas pipe valve 54 is increased, the flow rate of refrigerant through the low-pressure gas pipe valve 54 increases, thereby improving the cooling capacity of the indoor heat exchanger (S24).

[0152] Conversely, if the current value is less than the second set value, the air conditioner determines that the indoor heat exchanger is likely to be icing up, thereby reducing the opening of the low-pressure gas pipe valve 54.

[0153] If the opening degree of the low-pressure gas pipe valve 54 decreases, the pressure of the refrigerant passing through the low-pressure gas pipe valve 54 increases. At this time, the flow coefficient of the low-pressure gas pipe valve 54 can be greater than the flow coefficient of the first expansion valve 34 and the outdoor expansion valve of the outdoor unit 1. Therefore, the evaporation pressure of the indoor heat exchanger (indoor evaporation pressure) is controlled to be greater than the evaporation pressure of the outdoor heat exchanger (outdoor evaporation pressure), thus preventing the indoor heat exchanger from freezing (S25).

[0154] Then, the air conditioner determines whether the end conditions of the freeze prevention mode are met. If the end conditions of the freeze prevention mode are met, it proceeds to step S22. If the end conditions of the freeze prevention mode are not met, it determines whether an operation end command has been input.

[0155] Specifically, the freezing prevention mode termination condition may include a situation where the refrigerant temperature on the inlet side of the first heat exchanger 16 is above a third set value or a situation where the refrigerant temperature on the outlet side of the first heat exchanger 16 is above a third set value. Here, the third set value may be a temperature higher than the first set value and the second set value.

[0156] In other words, if the fourth or fifth temperature value is higher than the third set value, the air conditioner can terminate the freeze prevention mode.

[0157] If an operation end command is input, the air conditioner stops driving the compressor and the blower fan 14. If no operation end command is input, the process proceeds to step S26 (S26, S27, S28).

[0158] On the other hand, when the conditions for entering the freeze prevention mode are not met, the air conditioner can achieve a suitable level of cooling by controlling the opening of the first expansion valve 34. The air conditioner can determine whether the current cooling level of the indoor unit is the target level (set level). To this end, the air conditioner determines whether the difference between the fourth temperature value TH4 and the fifth temperature value TH5 is less than a reference value.

[0159] Here, the fourth temperature value TH4 represents the temperature sensed by the fourth temperature sensor T4, the fifth temperature value TH5 represents the temperature sensed by the fifth temperature sensor T5, and the reference value represents a preset temperature value (S29).

[0160] If the difference between the fourth and fifth temperature values ​​is less than the reference value, the air conditioner determines that the current cooling level of the indoor unit has not reached the target level, and increases the opening of the first expansion valve 34.

[0161] If the opening of the first expansion valve 34 is increased, the flow rate of refrigerant through the first expansion valve 34 will further increase, so the current cooling level of the indoor unit can be increased in a manner close to the target level (S30).

[0162] Conversely, if the difference between the fourth and fifth temperature values ​​is greater than the reference value, the air conditioner determines that the current cooling level of the indoor unit exceeds the target level and reduces the opening of the first expansion valve 34.

[0163] If the opening of the first expansion valve 34 decreases, the flow rate of refrigerant through the first expansion valve 34 decreases relatively, so the current cooling level of the indoor unit can be reduced in a manner close to the target level (S31).

[0164] Then, the air conditioner determines whether an operation end command has been input. If an operation end command has been input, the compressor and the blower fan 14 are stopped. If no operation end command has been input, the process proceeds to step S29 (S32).

[0165] According to the cooling mode M2 ​​described above, it is possible to prevent the indoor heat exchanger (dehumidifying coil) from icing up during prolonged operation in cooling mode. That is, in cooling mode M2, the indoor evaporation pressure can be controlled to be higher than the outdoor evaporation pressure by adjusting the opening of the low-pressure gas pipe valve 54, thereby preventing the indoor heat exchanger from icing up.

[0166] Figure 9 and Figure 10 This is a piping diagram illustrating the refrigerant flow in the cooling and dehumidification mode of the indoor unit in an embodiment of the present invention.

[0167] In this embodiment, the cooling and dehumidifying mode M3 includes: a first cooling and dehumidifying mode M3-1, in which the outdoor heat exchanger of the outdoor unit 10 is used as a condenser, and a portion of the plurality of indoor units 10 is used as an evaporator while another portion is used as a condenser; and a second cooling and dehumidifying mode M3-2, in which the outdoor heat exchanger is used as an evaporator, and a portion of the plurality of indoor units 10 is used as an evaporator while another portion is used as a condenser.

[0168] The cooling dehumidification mode can be called the "reheat dehumidification mode".

[0169] Below, refer to Figure 9 The first cooling and dehumidification mode, M3-1, will be explained.

[0170] In the first cooling and dehumidification mode M3-1, refrigerant flows from the outdoor unit 1 to the indoor unit 10 through the high-pressure gas pipe 40 and the liquid pipe 30, and the refrigerant in the indoor unit 10 flows to the outdoor unit 1 through the low-pressure gas pipe 50.

[0171] At this time, the low-pressure gas pipe valve 54, the second high-pressure gas pipe valve 48, the first expansion valve 34, the second expansion valve 38, and the supercooled expansion valve 76 are opened, and the first high-pressure gas pipe valve 44 is closed.

[0172] The outdoor heat exchanger of the outdoor unit 1 functions as a condenser, and the first heat exchanger 16 functions as an evaporator. The second heat exchanger 18 functions as a condenser and can heat the air passing through the second heat exchanger 18.

[0173] First, the flow of refrigerant will be explained with reference to the first heat exchanger 16.

[0174] If the air conditioner operates in the first cooling and dehumidifying mode M3-1, a portion of the high-temperature, high-pressure refrigerant compressed by the compressor of the outdoor unit 1 is condensed in the outdoor heat exchanger of the outdoor unit 1, and then flows into the indoor unit 10 through the liquid pipe 30. Furthermore, a portion of the refrigerant in the liquid pipe 30 flows into the subcooled expansion valve 76 through the branch pipe 74, while the remaining portion flows into the first expansion valve 34 through the first liquid pipe 32.

[0175] The refrigerant that has passed through the first expansion valve 34 is depressurized and flows into the first heat exchanger 16 where it is evaporated. The refrigerant discharged from the first heat exchanger 16 passes through the low-pressure gas pipe 50 and the low-pressure gas pipe valve 54. At this time, the low-pressure gas pipe valve 54 can be in a fully open state or a partially open state.

[0176] The refrigerant passing through the low-pressure gas pipe valve 54 flows along the low-pressure gas pipe 50 into the compressor of the outdoor unit 1.

[0177] In this embodiment, frost formation on the surface of the first heat exchanger 16 can be prevented by adjusting the opening of the low-pressure gas valve 54.

[0178] Next, the flow of refrigerant will be described with reference to the second heat exchanger 18.

[0179] If the air conditioner operates in cooling and dehumidification mode M3-1, the remaining portion of the high-temperature, high-pressure refrigerant compressed by the compressor of the outdoor unit 1 flows into the indoor unit 10 through the second high-pressure gas pipe 46. Furthermore, the refrigerant in the second high-pressure gas pipe 46 flows into the second heat exchanger 18 through the second high-pressure gas pipe valve 48 and is condensed.

[0180] The condensed refrigerant discharged from the second heat exchanger 18 flows through the second liquid line 36 and the second expansion valve 38 into the branch point 35 of the liquid line 30. The refrigerant flowing in from the branch point 35 merges with the refrigerant flowing in the first liquid line 32 and is depressurized at the first expansion valve 34, before flowing into the first heat exchanger 16 and evaporating.

[0181] Below, refer to Figure 10 The second cooling and dehumidification mode, M3-2, will be explained.

[0182] In the second cooling and dehumidification mode M3-2, refrigerant flows from the outdoor unit 1 to the indoor unit 10 through the high-pressure gas pipe 40, and the refrigerant in the indoor unit 10 flows to the outdoor unit 1 through the liquid pipe 30 and the low-pressure gas pipe 50.

[0183] At this time, the low-pressure gas pipe valve 54, the second high-pressure gas pipe valve 48, the first expansion valve 34, the second expansion valve 38, and the supercooled expansion valve 76 are opened, and the first high-pressure gas pipe valve 44 is closed.

[0184] The outdoor heat exchanger of the outdoor unit 1 and the first heat exchanger 16 function as evaporators. The second heat exchanger 18 functions as a condenser and can heat the air passing through the second heat exchanger 18.

[0185] If the air conditioner operates in the second cooling and dehumidification mode M3-2, the high-temperature, high-pressure refrigerant compressed by the compressor in the outdoor unit 1 flows into the indoor unit 10 through the second high-pressure gas pipe 46. Furthermore, the refrigerant in the second high-pressure gas pipe 46 flows into the second heat exchanger 18 through the second high-pressure gas pipe valve 48 and is condensed.

[0186] The condensed refrigerant discharged from the second heat exchanger 18 flows into the branch point 35 of the liquid pipe 30 after passing through the second liquid pipe 36 and the second expansion valve 38.

[0187] A portion of the refrigerant flowing in from the branch point 35 flows into the first liquid line 32 and is depressurized at the first expansion valve 34, after which it evaporates in the first heat exchanger 16. The evaporated refrigerant flows into the compressor of the outdoor unit 1 through the low-pressure gas line 50 and the first low-pressure gas line valve 54. At this time, the low-pressure gas line valve 54 can be in a fully open state or a partially open state.

[0188] In this embodiment, frost formation on the surface of the first heat exchanger 16 can be prevented by adjusting the opening of the low-pressure gas valve 54.

[0189] On the other hand, the remaining portion of the refrigerant flowing in from the branch point 35 flows into the supercooler 70 through the liquid pipe 30.

[0190] A portion of the refrigerant flowing into the supercooler 70 passes through the supercooling expansion valve 76 and supercools the refrigerant flowing in the liquid line 30 before merging with the low-pressure gas line 50 and flowing into the outdoor unit 1.

[0191] The remaining portion of the refrigerant flowing into the supercooler 70 flows into the outdoor unit 1 through the first liquid pipe 32.

[0192] The refrigerant flowing into the outdoor unit 1 is depressurized in the outdoor expansion device of the outdoor unit 1, and then evaporates in the outdoor heat exchanger of the outdoor unit 1. The evaporated refrigerant is recovered to the compressor of the outdoor unit 1.

[0193] In the cooling and dehumidification modes M3-1 and M3-2 as described above, a portion of the air that has been cooled and has become less humid by passing through the first heat exchanger 16 can be heated and flow into the room with a relatively lower humidity when passing through the second heat exchanger 18. Therefore, the air that has passed through the first heat exchanger 16 and the second heat exchanger 18 can flow into the room in a cooled and dehumidified state.

[0194] Figure 11 This is a flowchart illustrating the control method of an air conditioner in the cooling and dehumidification mode of the indoor unit in an embodiment of the present invention.

[0195] The following explanation uses the first cooling and dehumidification mode, in which the outdoor heat exchanger functions as the condenser, as an example.

[0196] Reference Figure 11 The air conditioner uses temperature and humidity information to determine the operating mode as cooling and dehumidification mode M3.

[0197] Temperature information may include the current outdoor air temperature value sensed by the first temperature sensor T1 and the set temperature value input by the user.

[0198] Humidity information may include the current humidity value of the outdoor air sensed by the humidity detection sensor HU and a set humidity value input by the user.

[0199] For example, if the user-inputted set temperature value is lower than the current outdoor air temperature value, and the user-inputted set humidity value is lower than the current outdoor air humidity value, the air conditioner can operate in cooling and dehumidifying mode M3 (S40).

[0200] If the unit is operated in cooling and dehumidification mode M3, the first high-pressure gas pipe valve 44 is closed, and the low-pressure gas pipe valve 54, the second expansion valve 38, and the second high-pressure gas pipe valve 48 are all opened. Therefore, the outdoor heat exchanger of the outdoor unit 1 functions as a condenser, the first heat exchanger 16 functions as an evaporator, and the second heat exchanger 18 functions as a condenser (S41).

[0201] The air conditioner can prevent the indoor heat exchanger (dehumidifying coil) from freezing by controlling the opening of the low-pressure gas pipe valve 54. To this end, the air conditioner determines whether the indoor heat exchanger's freeze prevention mode is activated.

[0202] Specifically, the conditions for entering the freeze prevention mode may include a situation where the refrigerant temperature on the inlet side of the first heat exchanger 16 is less than a first set value, or a situation where the refrigerant temperature on the outlet side of the first heat exchanger 16 is less than the first set value, or a situation where the temperature of the air passing through the first heat exchanger 16 is less than the first set value. Here, the first set value may be a preset temperature, which can be set by the user.

[0203] In other words, if the first temperature value, or the second temperature value, or the fourth temperature value, or the fifth temperature value is less than the first set value, the air conditioner can enter the freeze prevention mode (S42).

[0204] If the freeze prevention mode is entered, the air conditioner will determine whether the current value is greater than the second set value.

[0205] Here, the current value can be the temperature value sensed by the fourth temperature sensor T4 or the temperature value sensed by the fifth temperature sensor T5. Alternatively, the current value can be the average of the fourth and fifth temperature values. The second set value represents a preset temperature value (S43).

[0206] If the current value is greater than the second set value, the air conditioner determines that the possibility of icing in the indoor heat exchanger is small, thereby maintaining or increasing the opening of the low-pressure gas pipe valve 54.

[0207] If the opening degree of the low-pressure gas pipe valve 54 is increased, the flow rate of refrigerant through the low-pressure gas pipe valve 54 increases, thereby improving the cooling capacity of the indoor heat exchanger (S44).

[0208] Conversely, if the current value is less than the second set value, the air conditioner determines that the indoor heat exchanger is likely to be icing up, thereby reducing the opening of the low-pressure gas pipe valve 54.

[0209] If the opening degree of the low-pressure gas pipe valve 54 decreases, the pressure of the refrigerant passing through the low-pressure gas pipe valve 54 increases. At this time, the flow coefficient of the low-pressure gas pipe valve 54 can be greater than the flow coefficient of the first expansion valve 34 and the outdoor expansion valve of the outdoor unit 1. Therefore, the evaporation pressure of the indoor heat exchanger (indoor evaporation pressure) is controlled to be greater than the evaporation pressure of the outdoor heat exchanger (outdoor evaporation pressure), thus preventing the indoor heat exchanger from freezing (S45).

[0210] Then, the air conditioner determines whether the end conditions of the freeze prevention mode are met. If the end conditions of the freeze prevention mode are met, it proceeds to step S42. If the end conditions of the freeze prevention mode are not met, it determines whether an operation end command has been input.

[0211] Specifically, the freezing prevention mode termination condition may include a situation where the refrigerant temperature on the inlet side of the first heat exchanger 16 is above a third set value or a situation where the refrigerant temperature on the outlet side of the first heat exchanger 16 is above a third set value. Here, the third set value may be a temperature higher than the first set value and the second set value.

[0212] In other words, if the fourth or fifth temperature value is higher than the third set value, the air conditioner can terminate the freeze prevention mode.

[0213] If an operation end command is input, the air conditioner stops driving the compressor and the blower fan 14. If no operation end command is input, the process proceeds to step S46 (S46, S47, S48).

[0214] On the other hand, when the conditions for entering the freeze prevention mode are not met, the air conditioner can achieve a suitable level of cooling by controlling the opening of the first expansion valve 34. The air conditioner can determine whether the current cooling level of the indoor unit is the target level (set level). To this end, the air conditioner determines whether the difference between the fourth temperature value TH4 and the fifth temperature value TH5 is less than the reference value (S49).

[0215] If the difference between the fourth and fifth temperature values ​​is less than the reference value, the air conditioner determines that the current cooling level of the indoor unit has not reached the target level, and increases the opening of the first expansion valve 34.

[0216] If the opening of the first expansion valve 34 is increased, the flow rate of refrigerant through the first expansion valve 34 will further increase, so the current cooling level of the indoor unit can be increased in a manner close to the target level (S50).

[0217] Conversely, if the difference between the fourth and fifth temperature values ​​is greater than the reference value, the air conditioner determines that the current cooling level of the indoor unit exceeds the target level and reduces the opening of the first expansion valve 34.

[0218] If the opening of the first expansion valve 34 decreases, the flow rate of refrigerant through the first expansion valve 34 decreases relatively, so the current cooling level of the indoor unit can be reduced in a manner close to the target level (S51).

[0219] Then, the air conditioner determines whether an operation end command has been input. If an operation end command has been input, the compressor and the blower fan 14 are stopped. If no operation end command has been input, the process proceeds to step S49 (S52).

[0220] According to the cooling and dehumidifying mode M3 described above, the indoor heat exchanger (dehumidifying coil) can be prevented from icing up even when operating in cooling and dehumidifying mode for extended periods. That is, in cooling and dehumidifying mode M3, the indoor evaporation pressure is controlled to be higher than the outdoor evaporation pressure by adjusting the opening degree of the low-pressure gas pipe valve 54, thereby preventing the indoor heat exchanger from icing up.

[0221] Figure 12 This is a flowchart illustrating the control method of an air conditioner in the cooling and dehumidification mode of the indoor unit in an embodiment of the present invention.

[0222] Figure 12The method for controlling the opening of the second expansion valve 38 in the cooling and dehumidification mode M3 is provided.

[0223] Reference Figure 12 The air conditioner uses temperature and humidity information to determine the operating mode as cooling and dehumidification mode (S60).

[0224] If the system is operating in cooling and dehumidification mode M3, the first high-pressure gas pipe valve 44 is closed, and the low-pressure gas pipe valve 54, the second expansion valve 38, and the second high-pressure gas pipe valve 48 are all opened (S61).

[0225] The air conditioner can achieve a suitable level of cooling by controlling the opening of the second expansion valve 38. The air conditioner can determine whether the current cooling level of the indoor unit is at the target level (set level). To do this, the air conditioner determines whether the current value is less than the reference value (target value).

[0226] Here, the current value represents the temperature sensed by the third temperature sensor T3, and the reference value represents a preset temperature value (S62).

[0227] If the current value is less than the reference value, the air conditioner determines that the cooling level of the current indoor unit has not reached the target level, and increases the opening of the second expansion valve 38.

[0228] If the opening of the second expansion valve 38 is increased, the flow rate of refrigerant through the second expansion valve 38 will further increase, so the current cooling level of the indoor unit can be increased in a manner close to the target level (S63).

[0229] Conversely, if the current value is greater than the reference value, the air conditioner determines that the cooling level of the current indoor unit exceeds the target level and reduces the opening of the second expansion valve 38.

[0230] If the opening of the second expansion valve 38 is reduced, the flow rate of refrigerant through the second expansion valve 38 is relatively reduced, so the current cooling level of the indoor unit can be reduced in a manner close to the target level (S64).

[0231] On the other hand, the air conditioner determines whether an operation end command has been input through the input unit, and stops the operation of the compressor and the air supply fan 14 if an operation end command has been input, and proceeds to step S62 (S65, S66) if no operation end command has been input.

[0232] Figure 13 This is a piping diagram illustrating the refrigerant flow in the defrost mode of an embodiment of the present invention. Referring below... Figure 13 The defrost mode M4 is explained.

[0233] Defrost mode M4 is a mode used for a specified period of time during which the outdoor unit's outdoor heat exchanger is defrosted while the air conditioner is operating in heating mode M1. The refrigerant flow in defrost mode M4 is similar to that in the aforementioned cooling mode M1.

[0234] In defrost mode M4, the compressor frequency can be significantly increased to enhance the defrosting capability of the outdoor heat exchanger. This defrost mode M4 can also be used for oil recovery operation for compressor oil recovery.

[0235] In defrost mode M4, only the liquid line 30 and the low-pressure gas line 50 are used, and the refrigerant does not flow into the high-pressure gas line 40. In defrost mode M4, refrigerant flows from the outdoor unit 1 to the indoor unit 10 through the liquid line 30, and the refrigerant in the indoor unit 10 flows to the outdoor unit 1 through the low-pressure gas line 50.

[0236] At this time, the low-pressure gas pipe valve 54, the first expansion valve 34, and the supercooled expansion valve 76 are opened, while the first high-pressure gas pipe valve 44, the second high-pressure gas pipe valve 48, and the second expansion valve 38 are closed.

[0237] The outdoor heat exchanger of the outdoor unit 1 functions as a condenser, and the first heat exchanger 16 functions as an evaporator. Furthermore, refrigerant does not flow to the second heat exchanger 18.

[0238] If the air conditioner operates in defrost mode M4, the compressor frequency of the outdoor unit 1 increases significantly. The high-temperature, high-pressure refrigerant compressed by the compressor is condensed in the outdoor heat exchanger of the outdoor unit 1, and then flows into the indoor unit 10 through the liquid pipe 30. During this process, high-temperature, high-pressure gaseous refrigerant flows in the outdoor heat exchanger, thereby allowing the surface temperature of the outdoor heat exchanger to rise.

[0239] A portion of the refrigerant in the liquid pipe 30 flows into the subcooled expansion valve 76 through the branch pipe 74, while the remaining portion flows into the first expansion valve 34 through the first liquid pipe 32.

[0240] The refrigerant that has passed through the first expansion valve 34 is depressurized and flows into the first heat exchanger 16 where it is evaporated. The refrigerant discharged from the first heat exchanger 16 passes through the low-pressure gas pipe 50 and the low-pressure gas pipe valve 54. At this time, the low-pressure gas pipe valve 54 can be in a fully open state or a partially open state.

[0241] The refrigerant passing through the low-pressure gas pipe valve 54 flows along the low-pressure gas pipe 50 into the compressor of the outdoor unit 1.

[0242] Figure 14 This is a flowchart illustrating the control method of an air conditioner in defrost mode according to an embodiment of the present invention.

[0243] Reference Figure 14 The air conditioner can operate in defrost mode M4. This can be understood as an operating mode used to prevent the outdoor heat exchanger from freezing and cracking while operating in heating mode.

[0244] The defrost mode can be executed by user input or under set defrost operation conditions. For example, the air conditioner can perform defrost operation based on the temperature sensed by a temperature sensor installed on the outdoor heat exchanger of the outdoor unit (S70).

[0245] If operating in defrost mode M4, the first high-pressure gas valve 44 is closed, the low-pressure gas valve 54 is opened, and the second expansion valve 38 and the second high-pressure gas valve 48 are closed. Thus, the outdoor heat exchanger of the outdoor unit 1 functions as a condenser, and the first heat exchanger 16 functions as an evaporator. The second heat exchanger 18 is not used (S71).

[0246] During operation in defrost mode M4, the air conditioner can prevent the indoor heat exchanger from freezing by controlling the opening of the low-pressure gas pipe valve 54. To this end, the air conditioner determines whether the conditions for entering the freeze prevention mode of the indoor heat exchanger have been met.

[0247] Specifically, the conditions for entering the freeze prevention mode may include a situation where the refrigerant temperature on the inlet side of the first heat exchanger 16 is less than a first set value, or a situation where the refrigerant temperature on the outlet side of the first heat exchanger 16 is less than the first set value, or a situation where the temperature of the air passing through the first heat exchanger 16 is less than the first set value. Here, the first set value may be a preset temperature, which can be set by the user.

[0248] In other words, if the first temperature value, or the second temperature value, or the fourth temperature value, or the fifth temperature value is less than the first set value, the air conditioner can enter the freeze prevention mode (S72).

[0249] If the freeze prevention mode is entered, the air conditioner will determine whether the current value is greater than the second set value.

[0250] Here, the current value can be the temperature value sensed by the fourth temperature sensor T4 or the temperature value sensed by the fifth temperature sensor T5. Alternatively, the current value can be the average of the fourth and fifth temperature values. The second set value represents a preset temperature value (S73).

[0251] If the current value is greater than the second set value, the air conditioner determines that the possibility of icing in the indoor heat exchanger is small, thereby maintaining or increasing the opening of the low-pressure gas pipe valve 54.

[0252] If the opening degree of the low-pressure gas pipe valve 54 is increased, the flow rate of refrigerant through the low-pressure gas pipe valve 54 increases, thereby improving the cooling capacity of the indoor heat exchanger (S74).

[0253] Conversely, if the current value is less than the second set value, the air conditioner determines that the indoor heat exchanger is likely to be icing up, thereby reducing the opening of the low-pressure gas pipe valve 54.

[0254] If the opening degree of the low-pressure gas pipe valve 54 decreases, the pressure of the refrigerant passing through the low-pressure gas pipe valve 54 increases. At this time, the flow coefficient of the low-pressure gas pipe valve 54 can be greater than the flow coefficients of the first expansion valve 34 and the outdoor expansion valve of the outdoor unit. Thus, the evaporation pressure of the indoor heat exchanger is controlled to be greater than the evaporation pressure of the outdoor heat exchanger, thereby preventing the indoor heat exchanger from freezing (S75).

[0255] Then, the air conditioner determines whether the end conditions of the freeze prevention mode are met. If the end conditions of the freeze prevention mode are met, it proceeds to step S72. If the end conditions of the freeze prevention mode are not met, it determines whether a defrost operation end command has been input.

[0256] Specifically, the freezing prevention mode termination condition may include a situation where the refrigerant temperature on the inlet side of the first heat exchanger 16 is above a third set value or a situation where the refrigerant temperature on the outlet side of the first heat exchanger 16 is above a third set value. Here, the third set value may be a temperature higher than the first set value and the second set value.

[0257] In other words, if the fourth or fifth temperature value is higher than the third set value, the air conditioner can terminate the freeze prevention mode.

[0258] When a defrosting operation end command is input, the air conditioner can end the defrosting operation and switch to heating mode (S76, S77, S78).

[0259] On the other hand, when the conditions for entering the freeze prevention mode are not met, the air conditioner can achieve a suitable level of cooling by controlling the opening of the first expansion valve 34. The air conditioner can determine whether the current cooling level of the indoor unit is the target level (set level). To this end, the air conditioner determines whether the difference between the fourth temperature value TH4 and the fifth temperature value TH5 is less than a reference value.

[0260] Here, the fourth temperature value TH4 represents the temperature sensed by the fourth temperature sensor T4, the fifth temperature value TH5 represents the temperature sensed by the fifth temperature sensor T5, and the reference value represents a preset temperature value (S79).

[0261] If the difference between the fourth and fifth temperature values ​​is less than the reference value, the air conditioner determines that the current cooling level of the indoor unit has not reached the target level, and increases the opening of the first expansion valve 34.

[0262] If the opening of the first expansion valve 34 is increased, the flow rate of refrigerant through the first expansion valve 34 will further increase, so the current cooling level of the indoor unit can be increased in a manner close to the target level (S80).

[0263] Conversely, if the difference between the fourth and fifth temperature values ​​is greater than the reference value, the air conditioner determines that the current cooling level of the indoor unit exceeds the target level and reduces the opening of the first expansion valve 34.

[0264] If the opening of the first expansion valve 34 decreases, the flow rate of refrigerant through the first expansion valve 34 decreases relatively, so the current cooling level of the indoor unit can be reduced in a manner close to the target level (S81).

[0265] Then, the air conditioner determines whether a defrosting operation end command has been input, and ends the defrosting operation if a defrosting operation end command has been input, and proceeds to step S79 (S82) if no defrosting operation end command has been input.

[0266] According to the defrosting mode M4 described above, the outdoor heat exchanger can be prevented from freezing even when operating in heating mode for extended periods.

[0267] Specifically, when the compressor frequency is increased to improve the defrosting capacity of the outdoor heat exchanger during operation in defrost mode M4, icing may occur in the indoor heat exchanger due to a decrease in evaporation pressure. Therefore, in defrost mode M4 of this invention, the opening degree of the low-pressure gas pipe valve 54 can be adjusted to ensure that the indoor evaporation pressure is higher than the outdoor evaporation pressure, thereby preventing icing of the indoor heat exchanger.

[0268] The preferred embodiments of the present invention have been illustrated and described above. However, the present invention is not limited to the specific embodiments described above. Without departing from the spirit of the present invention as claimed in the claims, those skilled in the art can make various modifications. Such modifications should not be understood separately from the technical concept or prospect of the present invention.

Claims

1. An air conditioner, wherein, include: The casing has an internal airflow path for outdoor air to flow into the interior; A first heat exchanger is configured in the air flow path, and refrigerant flows in the first heat exchanger to exchange heat between the flowing air and the refrigerant. A second heat exchanger is disposed downstream of the first heat exchanger in the air flow path, and refrigerant selectively flows in the second heat exchanger to exchange heat between the flowing air and the refrigerant. A liquid pipe is connected to the first heat exchanger and the second heat exchanger respectively, and liquid refrigerant flows in the liquid pipe; A high-pressure gas pipe is connected to the first heat exchanger and the second heat exchanger respectively, and gaseous refrigerant flows in the high-pressure gas pipe; A low-pressure gas pipe connects the outdoor unit to the first heat exchanger; A high-pressure gas valve is installed in the high-pressure gas pipe; A low-pressure gas pipe valve is installed in the low-pressure gas pipe; An expansion valve is installed in the liquid pipe; as well as When the control unit enters the freeze-crack prevention mode for the first heat exchanger, it controls the opening degree of the low-pressure gas pipe valve based on the temperature of the refrigerant flowing in the first heat exchanger.

2. The air conditioner according to claim 1, wherein, The control unit controls the opening degree of the low-pressure gas pipe valve based on the refrigerant temperature on the inlet side or the refrigerant temperature on the outlet side of the first heat exchanger.

3. The air conditioner according to claim 2, wherein, The control unit determines whether the refrigerant temperature on the inlet side of the first heat exchanger is lower than a set value. When the refrigerant temperature at the inlet side of the first heat exchanger is less than a set value, the control unit reduces the opening of the low-pressure gas pipe valve.

4. The air conditioner according to claim 3, wherein, When the refrigerant temperature at the inlet side of the first heat exchanger is above a set value, the control unit increases or maintains the opening of the low-pressure gas pipe valve.

5. The air conditioner according to claim 2, wherein, The control unit determines whether the refrigerant temperature on the outlet side of the first heat exchanger is lower than a set value. When the refrigerant temperature at the outlet side of the first heat exchanger is lower than a set value, the control unit reduces the opening of the low-pressure gas pipe valve.

6. The air conditioner according to claim 5, wherein, When the refrigerant temperature at the outlet side of the first heat exchanger is above a set value, the control unit increases or maintains the opening of the low-pressure gas pipe valve.

7. The air conditioner according to claim 1, wherein, The control unit determines whether the first heat exchanger meets the conditions for entering the freeze-crack prevention mode. When the conditions for entering the freeze-crack prevention mode are met, the control unit controls the opening degree of the low-pressure gas pipe valve based on the temperature of the refrigerant flowing in the first heat exchanger.

8. The air conditioner according to claim 7, wherein, The conditions for entering the freeze-crack prevention mode include the refrigerant temperature on the inlet side of the first heat exchanger being less than a first set value or the refrigerant temperature on the outlet side of the first heat exchanger being less than a first set value.

9. The air conditioner according to claim 8, wherein, If the conditions for entering the freeze-cracking prevention mode are met, the control unit determines whether the refrigerant temperature on the inlet side of the first heat exchanger is less than a second set value that is smaller than the first set value. When the refrigerant temperature at the inlet side of the first heat exchanger is less than the second set value, the control unit reduces the opening of the low-pressure gas pipe valve.

10. The air conditioner according to claim 9, wherein, When the refrigerant temperature at the inlet side of the first heat exchanger is above the second set value, the control unit increases or maintains the opening of the low-pressure gas pipe valve.

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