Air conditioner and method of controlling the same

An air conditioner and a method of controlling the same are provided. The air conditioner includes first and second compressors capable of performing multi-stage compression, a condenser for condensing a refrigerant compressed in the first and second compressors, a refrigerant separation device for separating the refrigerant to be injected to the first or second compressor of the refrigerant condensed in the condenser, injection tubes extending from the refrigerant separation device to the first and second compressors to guide injection of the refrigerant, a main expansion device disposed at an outlet-side of the refrigerant separation device to decompress the refrigerant, an evaporator for evaporating the refrigerant decompressed in the main expansion device, a valve device disposed at an outlet-side of the first compressor to guide the refrigerant compressed in the first compressor to the condenser or the second compressor, and a bypass tube extending from the valve device to an suction-side of the second compressor.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. 119 and 35 U.S.C. 365 to Korean Patent Application No. 10-2014-0105907 (filed on Aug. 14, 2014), which is hereby incorporated by reference in its entirety.

BACKGROUND

The present disclosure relates to an air conditioner.

Air conditioners are household electronic appliances for maintaining indoor air in the most suitable state according to uses and purposes. For example, the air conditioners adjust indoor spaces in a cooling condition in summer and also in a warm heating condition in winter. Also, the air conditioners adjust humidity of the indoor space and indoor air in a pleasant clean condition. In detail, an air conditioner drives a refrigeration cycle in which compression, condensation, expansion, and evaporation processes of a refrigerant are performed to cool or heat the indoor space.

Such an air conditioner may be classified into a separated-type air conditioner in which an indoor unit is separated from an outdoor unit and an integrated-type air conditioner in which the indoor unit is integrated with the outdoor unit as one device. The outdoor unit includes an outdoor heat exchanger for heat-exchanging with outdoor air, and the indoor unit includes an indoor heat exchanger for heat-exchanging with indoor air. The air conditioner may switchably operate in a cooling or heating mode.

When the air conditioner operates in a cooling mode, the outdoor heat exchanger acts as a condenser, and the indoor heat exchanger acts as an evaporator. On the other hand, when the air conditioner operates in a heating mode, the outdoor heat exchanger acts as an evaporator, and the indoor heat exchanger acts as a condenser.

The air conditioner may further include a supercooling heat exchanger for supercooling a refrigerant condensed in the condenser. The main refrigerant that is heat-exchanged in the supercooling heat exchanger may be decompressed and evaporated in the evaporator, and a branch refrigerant that is heat-exchanged in the supercooling heat exchanger may be injected to the compressor. According to the structure of the air conditioner, multi-stage compression may be performed in the compressor.

The applicant of the present invention has filed an application in regard to the above-described idea.

However, according to the related art, since the refrigerant is compressed in only three-stages, the compressor has operation efficiency that is limited to less than a predetermined value.

SUMMARY

Embodiments provide an air conditioner in which a plurality of compressors perform a parallel operation or a series operation according to an operation mode.

In one embodiment, an air conditioner includes: first and second compressors capable of performing multi-stage compression; a condenser for condensing a refrigerant compressed in the first and second compressors; a refrigerant separation device for separating the refrigerant to be injected to the first or second compressor of the refrigerant condensed in the condenser; injection tubes extending from the refrigerant separation device to the first and second compressors to guide injection of the refrigerant; a main expansion device disposed at an outlet-side of the refrigerant separation device to decompress the refrigerant; an evaporator for evaporating the refrigerant decompressed in the main expansion device; a valve device disposed at an outlet-side of the first compressor to guide the refrigerant compressed in the first compressor to the condenser or the second compressor; and a bypass tube extending from the valve device to an suction-side of the second compressor.

Also, the valve device may include: an inlet to which the refrigerant compressed in the first compressor is introduced; a first outlet from which the refrigerant compressed in the compressor is discharged to an inlet-side of the condenser; and a second outlet from which the refrigerant compressed in the first compressor is discharged to the bypass tube.

Also, the air conditioner may further include: a compressor branch part for dividing the refrigerant evaporated in the evaporator to allow the refrigerant to flow to the first and second compressors; a first suction tube extending from the compressor branch part to the first compressor; and a second suction tube extending from the compressor branch part to the second compressor.

Also, the bypass tube may extend from second outlet of the valve device to the second suction tube.

Also, the air conditioner may further include: a valve connection tube connected to the first outlet of the valve device; a discharge tube for discharging the refrigerant compressed in the second compressor; and a combination part at which the valve connection tube is combined with the discharge tube.

Also, the injection tube may include a plurality of injection tubes through which a branch refrigerant that is heat-exchanged in the refrigerant separation device is divided to flow, and a refrigerant in one of the plurality of injection tubes may be injected to the first compressor, and a refrigerant in the other injection tube may be injected to the second compressor.

Also, the refrigerant separation device may include: a first supercooling heat exchanger in which the refrigerant condensed in the condenser is heat-exchanged with a first branch refrigerant divided from the refrigerant; and a second supercooling heat exchanger in which the refrigerant that is heat-exchanged in the first supercooling heat exchanger is heat-exchanged with a second branch refrigerant divided from the heat-exchanged refrigerant.

Also, the injection tube may include first and second injection tubes through which the first branch refrigerant that is heat-exchanged in the first supercooling heat exchanger is divided to flow, and the refrigerant in the first injection tube may be injected to the first compressor, and the refrigerant in the second injection tube may be injected to the second compressor.

Also, the injection tube may include third and fourth injection tubes through which the second branch refrigerant that is heat-exchanged in the second supercooling heat exchanger is divided to flow, and the refrigerant in the third injection tube may be injected to the first compressor, and the refrigerant in the fourth injection tube may be injected to the second compressor.

Also, the air conditioner may further include: a first injection expansion device disposed on the first injection tube to decompress the refrigerant; and a second injection expansion device disposed on the third injection tube to decompress the refrigerant.

Also, the refrigerant decompressed in the first injection expansion device may be injected to a high pressure-side of the first compressor, and the refrigerant decompressed in the second injection expansion device may be injected to a low pressure-side of the first compressor.

Also, the refrigerant in the second injection tube may be injected to a high pressure-side of the second compressor, and the refrigerant in the fourth injection tube may be injected to a low pressure-side of the second compressor.

Also, the valve device may operate in a first operation mode so that the refrigerant compressed in the first compressor is mixed with the refrigerant compressed in the second compressor, and the valve device may operate in a second operation mode so that the refrigerant compressed in the first compressor is suctioned into the second compressor via the bypass tube.

Also, the refrigerant separation device may include a phase separator.

Also, the air conditioner may include a check valve disposed at a suction-side of the second compressor to restrict the refrigerant from flowing from the bypass tube to a suction-side of the first compressor.

In another embodiment, a method of controlling an air conditioner including first and second compressors, a condenser, a main expansion device, and an evaporator includes: driving the first and second compressors; determining an action mode of a valve device disposed at an outlet-side of the first compressor according to an operation mode; dividing the refrigerant passing through the condenser by opening a first supercooling expansion device to allow the refrigerant to be heat-exchanged in a first supercooling heat exchanger and to flow through a first injection tube; and dividing the refrigerant passing through the supercooling heat exchanger by opening a second supercooling expansion device to allow the refrigerant to be heat-exchanged in a second supercooling heat exchanger and to flow through a third injection tube, wherein, when a first operation mode of the operation mode is performed, each of the first and second compressors performs a three-stage compression with respect to the refrigerant, and when a second operation mode is performed, the refrigerant successively passes through the first and second compressors and thus is compressed in five stages.

Also, the action mode of the valve device may include: a first action mode in which the refrigerant compressed in the first compressor is discharged to an inlet-side of the condenser when the first operation mode is performed; and a second action mode in which the refrigerant compressed in the first compressor is discharged to a suction-side of the second compressor when the second operation mode is performed.

Also, when the refrigerant flows through the first injection tube, the refrigerant may be decompressed in a first injection expansion device and injected to a high pressure-side of the first compressor.

Also, when the refrigerant flows through the third injection tube, the refrigerant may be decompressed in a second injection expansion device and injected to a low pressure-side of the first compressor.

Also, the first operation mode may be an operation mode in which an operation load higher than a preset load is needed, and the second operation mode may be an operation mode in which an operation load less than a preset load is needed.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring toFIG. 1, in an air conditioner10according to the first embodiment, a refrigeration cycle in which a refrigerant circulates is driven.

The air conditioner10includes a plurality of compressors110and120for compressing the refrigerant, a condenser150in which the refrigerant compressed in the plurality of compressors110and120is condensed, main expansion devices161and165for selectively expanding the refrigerant condensed in the condenser150, an evaporator190for evaporating the refrigerant expanded in the main expansion devices161and165, and a refrigerant tube20for connecting the above-described components to each other to guide a flow of the refrigerant.

The plurality of compressors110and120has a structure in which multi-stage compression is performed. For example, the plurality of compressors110and120may include a scroll compressor in which a compression space where an operation gas is absorbed and discharged is defined between an orbiting scroll and a fixed scroll, and the refrigerant is compressed while the orbiting scroll rotates along the fixed scroll or a rotary compressor in which a compression space where an operation gas is absorbed and discharged is defined between a roller that eccentrically rotates and a cylinder, and the refrigerant is compressed while the roller eccentrically rotates along an inner wall of the cylinder.

In detail, the plurality of compressors110and120include a first compressor110and a second compressor120which operate in parallel or series.

The parallel operation represents an operation in which the refrigerant is divided into the first and second compressors110and120and compressed in each of the first and second compressors110and120and then is mixed with each other to be introduced into the condenser150. On the other hand, the series operation represents an operation in which the refrigerant is compressed in the first compressor110and suctioned to be further compressed in the second compressor120and then is introduced into the condenser150.

The first compressor110includes three compression parts111,113, and115. The three compression parts111,113, and115include a first compression part111, a second compression part113for additionally compressing the refrigerant compressed in the first compressor111, and a third compression part115for additionally compressing the refrigerant compressed in the second compression part113.

The second compressor120includes three compression parts121,123, and125. The three compression parts121,123, and125include a first compression part121, a second compression part123for additionally compressing the refrigerant compressed in the first compressor121, and a third compression part125for additionally compressing the refrigerant compressed in the second compression part123.

The refrigerant tube20includes a first suction tube110afor guiding suction of the refrigerant to the first compressor110and a second suction tube120afor guiding suction of the refrigerant to the second compressor120. Also, the air conditioner10includes a compressor branch part167for dividing the refrigerant into the first suction tube110aand the second suction tube120a.

A first check valve120bfor allowing the refrigerant to flow in one direction from the compressor branch part167to the second compressor120may be disposed in the second suction tube120a. A flow of the refrigerant from a suction-side of the second compressor120to the compressor branch part167may be limited by the first check valve120b.

The refrigerant tube20may further include a first discharge tube131for guiding discharge of the refrigerant compressed in the first compressor110and a second discharge tube132for guiding discharge of the refrigerant compressed in the second compressor120.

Also, a second check valve132afor allowing the refrigerant discharge from the second compressor120to flow to the condenser150in one direction may be disposed in the second discharge tube132. A flow of the refrigerant from a first combination part134to a discharge-side of the second compressor120may be limited by the second check valve132a.

The air conditioner10may further include a valve device140for guiding the refrigerant in the discharge tube131toward the condenser150or the suction-side of the second compressor120. For example, the valve device140may include a three-way valve having one inlet and two outlets. The first discharge tube131is connected to an inlet140aof the valve device140.

The refrigerant tube20may further include a valve connection tube133connected to a first outlet140bof the two outlets140band140cof the valve device140and a bypass tube145connected to a second outlet140cof the two outlets140band140c.

A third check valve133afor allowing the refrigerant discharged from the first outlet140bof the valve device140to flow toward the condenser150in one direction may be disposed in the valve connection tube133. A flow of the refrigerant from the first combination part134to the first outlet140bmay be limited by the third check valve133a.

The air conditioner10may further include the first combination part134at which the refrigerant flowing through the valve connection tube133is mixed with the refrigerant flowing through the second discharge tube132.

The refrigerant flowing through the first discharge tube131may be introduced into the valve connection tube133through the valve device140and mixed with the refrigerant in the second discharge tube132and thus be introduced into the condenser150. That is, the refrigerant introduced into the valve device140through the inlet140amay be discharged to the valve connection tube133through the first outlet140b. Here, an action mode of the valve device140may be called a “first action mode”.

In the first action mode of the valve device140, the air conditioner10may perform the parallel operation mode (a first operation mode) of the first and second compressors110and120.

The bypass tube145may be understood as a tube for guiding the refrigerant discharged through the second outlet140cof the valve device140toward the suction-side of the second compressor120.

The bypass tube145may have one side portion that is connected to the second outlet140cof the valve device140and the other side portion that is connected to a second combination part148of the second suction tube120a. The second combination part148may be understood as a portion disposed on one point of the second suction tube120aand to which the bypass tube145is connected. The refrigerant flowing through the bypass tube145may be mixed with the refrigerant in the second suction tube120aand thus be suctioned into the second compressor120.

The first check valve120bmay restrict the refrigerant from flowing from the bypass tube145toward the compressor branch part167, that is, toward the first compressor110.

That is, the refrigerant introduced into the valve device140through the inlet140amay be discharged to the bypass tube145through the second outlet140c. Here, an action mode of the valve device140may be called a “second action mode”.

In the second action mode of the valve device140, the air conditioner10may perform the series operation mode (a second operation mode) of the first and second compressors110and120.

The condenser150includes a condensation tube151through which the refrigerant compressed in the first compressor110or the second compressor120, a condensation fin153coupled to the condensation tube151, and a condensation fan155generating a flow of air.

The main expansion devices161and165include a first main expansion device161disposed at an outlet-side of the condenser150. In the first and second operation modes of the air conditioner10, the first main expansion device161may be fully opened.

The air conditioner10includes a plurality of supercooling heat exchangers170and180allowing the refrigerant passing through the condenser150to be supercooled. The supercooling heat exchangers170and180include a first supercooling heat exchanger170and a second supercooling heat exchanger180.

In the first supercooling heat exchanger170, the refrigerant (hereinafter, referred to as a “first main refrigerant) passing through the condenser150may be heat-exchanged with the refrigerant (hereinafter, referred to as a “first branch refrigerant”) divided from the first main refrigerant.

In detail, the air conditioner10may further include a first branch tube171for allowing at least one portion of the first branch refrigerant of the first main refrigerant passing through the condenser150to bypass and a first supercooling expansion device173disposed on the first branch tube171to decompress the first branch refrigerant.

The first branch refrigerant decompressed in the first supercooling expansion device173may be introduced into the supercooling heat exchanger170and heat-exchanged with the first main refrigerant. In this process, the first branch refrigerant may be evaporated, and the first main refrigerant may be supercooled.

The air conditioner10may further include a first branch part174for dividing the refrigerant in the first branch tube171to allow the refrigerant to flow into the first and second compressors110and120.

The air conditioner10may further include a first injection tube175extending from the first branch part174to the first compressor110and a second injection tube176extending from the first branch part174to the second compressor120.

The first injection tube175is connected to a first injection port117of the first compressor110. The refrigerant in the first injection tube175may be injected to the first compressor110through the first injection port117and mixed with the refrigerant compressed in the second compression part113of the first compressor110and thus be introduced into the third compression part115.

The second injection tube176is connected to a second injection port127of the second compressor120. The refrigerant in the second injection tube176may be injected to the second compressor120through the second injection port127and mixed with the refrigerant compressed in the second compression part123of the second compressor120and thus be introduced into the third compression part125.

The first injection tube175may further include a first injection expansion device177for decompressing the refrigerant when the air conditioner10performs the second operation mode. When the air conditioner10performs the first operation mode, the first injection expansion device177may be fully opened, and thus, the refrigerant may not be decompressed.

In the second supercooling heat exchanger180, the refrigerant (hereinafter, referred to as a “second main refrigerant”) passing through the first supercooling heat exchanger170may be heat-exchanged with the refrigerant (hereinafter, referred to as a “second branch refrigerant) divided from the second main refrigerant.

In detail, the air conditioner10may further include a second branch tube181for allowing at least one portion of the second branch refrigerant of the second main refrigerant passing through the first supercooling heat exchanger170to bypass and a second supercooling expansion device183disposed on the second branch tube181to decompress the second branch refrigerant.

The second branch refrigerant decompressed in the second supercooling expansion device183may be introduced into the supercooling heat exchanger180and heat-exchanged with the second main refrigerant. In this process, the second branch refrigerant may be evaporated, and the second main refrigerant may be supercooled.

The air conditioner10may further include a second branch part184for dividing the refrigerant of the second branch tube181to allow the refrigerant to flow into the first and second compressors110and120.

The air conditioner10may further include a third injection tube185extending from the second branch part184to the first compressor110and a fourth injection tube186extending from the second branch part184to the second compressor120.

The third injection tube185is connected to a third injection port119of the first compressor110. The refrigerant in the third injection tube185may be injected to the first compressor110through the third injection port119and mixed with the refrigerant compressed in the first compression part111of the first compressor110and thus be introduced into the second compression part113.

The fourth injection tube186is connected to a fourth injection port129of the second compressor120. The refrigerant of the fourth injection tube186may be injected to the second compressor120through the fourth injection port129and mixed with the refrigerant compressed in the first compression part121of the second compressor120and thus be introduced into the second compression part123.

Shortly, the refrigerant flowing through the third injection tube185may be injected to a low pressure-side of the first compressor110, and the refrigerant flowing through the first injection tube175may be injected to a high pressure-side of the first compressor110.

On the other hand, the refrigerant flowing through the fourth injection tube186may be injected to a low pressure-side of the second compressor120, and the refrigerant flowing through the second injection tube176may be injected to a high pressure-side of the second compressor120.

The third injection tube185may further include a second injection expansion device187for decompressing the refrigerant when the air conditioner10performs the second operation mode. When the air conditioner performs the first operation mode, the second injection expansion device187may be fully opened, and thus the refrigerant may not be decompressed.

The second main expansion device165for decompressing the refrigerant is disposed at an outlet-side of the second supercooling heat exchanger180. The second main refrigerant passing through the second supercooling heat exchanger180may be decompressed in the second main expansion device165when the air conditioner10performs the first and second operation modes.

The refrigerant decompressed in the second main expansion device165may be introduced into the evaporator190and then be evaporated. The evaporator190includes an evaporation tube191through which the refrigerant flows, an evaporation fin193coupled to the evaporation tube191, and an evaporation fan195generating a flow of the air.

The refrigerant passing through the evaporator190may be suctioned into the first compressor110or the second compressor120via the compressor branch part167.

In detail, when the air conditioner10performs the first operation mode, the refrigerant may be divided from the compressor branch part167into the first and second compressors110and120. On the other hand, when the air conditioner10performs the second operation mode, the refrigerant may be suctioned into the first compressor110from the compressor branch part167but be limited to be suctioned into the second compressor120.

FIG. 2is a system view illustrating a state in which a refrigerant flows when the air conditioner performs a first operation mode according to the first embodiment, andFIG. 3is a flowchart showing a method of controlling the air conditioner when the air conditioner performs the first operation mode according to the first embodiment.

A method of controlling the air conditioner and the flow of the refrigerant when the air conditioner10performs the first operation mode according to the first embodiment will be described with reference toFIGS. 2 and 3.

When the first operation mode of the air conditioner10starts, the first and second compressors110and120are driven. Here, the “first operation mode” may be understood as a “high-load operation mode” that operates when a lot of circulation amounts of the refrigerant are required due to a high operation load of the air conditioner, that is, an operation mode in which an operation load higher than a preset load is needed.

When the first and second compressors110and120are driven, the refrigerant may be divided to flow through the first and second suction tubes120aand120band then be suctioned into the first and second compressors110and120. That is, in operation S11, the first and second compressors110and120may operate in parallel.

The refrigerant compressed in the first compressor110may be introduced into the valve device140to flow to the first branch part134through the valve connection tube133. Here, in operation S12, the valve device140is controlled in the first action mode, and the refrigerant introduced into the valve device140may be restricted to flow into the bypass tube145and discharged to the valve connection tube133through the first outlet140b.

Also, the refrigerant compressed in the second compressor120may flow through the second discharge tube132and be mixed with the refrigerant discharged from the first outlet140in the first combination part134.

The refrigerant mixed in the first combination part134is condensed in the condenser150to flow through the first main expansion device. Here, in operation S13, the first main expansion device161may be fully opened, and thus, the refrigerant may not be decompressed while passing through the first main expansion device161.

The refrigerant (the first main refrigerant) passing through the first main expansion device161may be introduced into the first supercooling heat exchanger170. At least one portion of the first branch refrigerant of the first main refrigerant may be divided to flow into the first branch tube171, and the first main refrigerant may be heat-exchanged with the first branch refrigerant in the first supercooling heat exchanger170.

Here, in operation S14, the first supercooling expansion device173may be opened in a predetermined opening degree so that the first branch refrigerant flowing through the first branch tube171is decompressed.

In the process in which the decompressed first branch refrigerant is heat-exchanged with the first main refrigerant, the first branch refrigerant may be evaporated, and the first main refrigerant may be supercooled. The evaporated first branch refrigerant may be divided from the first branch part174to flow into the first injection tube175and the second injection tube176.

The refrigerant flowing through the first injection tube175may be injected to the first injection port117of the first compressor110through the first injection expansion device177. The refrigerant that is injected to the first injection port117may be mixed with the refrigerant compressed in the second compression part113of the first compressor110. Thus, the injection of the refrigerant to the first injection port117may be called a “high pressure-side injection of the first compressor110”.

Here, in operation S15, the first injection expansion device177may be fully opened, and thus, the refrigerant flowing through the first injection tube175may not be decompressed while passing through the first injection expansion device177.

The refrigerant flowing through the second injection tube176may be injected to the second injection port127of the second compressor120. The refrigerant that is injected to the second injection port127may be mixed with the refrigerant compressed in the second compression part123of the second compressor120. The injection of the refrigerant to the second injection port127may be called a “high pressure-side injection of the second compressor120”.

The refrigerant (the second main refrigerant) passing through the first supercooling heat exchanger170may be introduced into the second supercooling heat exchanger180. At least one portion of the second branch refrigerant of the second main refrigerant may be divided to flow into the second branch tube181, and the second main refrigerant may be heat-exchanged with the second branch refrigerant in the second supercooling heat exchanger180.

Here, in operation S16, the second supercooling expansion device183may be opened in a predetermined opening degree so that the second branch refrigerant flowing through the second branch tube181is decompressed.

In the process in which the decompressed second branch refrigerant is heat-exchanged with the second main refrigerant, the second branch refrigerant may be evaporated, and the second main refrigerant may be supercooled. The evaporated second branch refrigerant may be divided from the second branch part184to flow into the third and fourth injection tubes185and186.

The refrigerant flowing through the third injection tube185may be injected to the third injection port119of the first compressor110through the second injection expansion device187. The refrigerant that is injected to the third injection port119may be mixed with the refrigerant compressed in the first compression part111of the first compressor110. Thus, the injection of the refrigerant to the third injection port119may be called a “low pressure-side injection of the first compressor110”.

Here, in operation S17, the second injection expansion device187may be fully opened, and thus, the refrigerant flowing through the third injection tube185may not be decompressed while passing through the second injection expansion device187.

The refrigerant flowing through the fourth injection tube186may be injected to the fourth injection port129of the second compressor120. The refrigerant that is injected to the fourth injection port129may be mixed with the refrigerant compressed in the first compression part121of the second compressor120. The injection of the refrigerant to the fourth injection port129may be called a “low pressure-side injection of the second compressor120”.

Like this, the refrigerant passing through the first and second supercooling heat exchangers170and180may be injected to the low pressure-side and high pressure-side of each of the first and second compressors110and120, that is, injected two times, and thus, three-stage compression may be performed in each of the compressors110and120.

The refrigerant passing through the second supercooling heat exchanger180may be introduced into the evaporator180through the second main expansion device165. Here, in operation S18, the second main expansion device165may be opened in a predetermined opening degree so that the refrigerant is decompressed.

The refrigerant evaporated in the evaporator190may be divided from the compressor branch part167, and a portion of the refrigerant of the divided refrigerant may be suctioned into the first compressor110through the first suction tube110a, and the rest of the refrigerant may be suctioned into the second compressor120through the second suction tube120a.

FIG. 4is a system view illustrating a state in which the refrigerant flows when the air conditioner performs a second operation mode according to the first embodiment, andFIG. 5is a flowchart showing a method of controlling the air conditioner when the air conditioner performs a second operation mode according to the first embodiment.

A method of controlling the air conditioner and a flow of the refrigerant when the air conditioner10performs the second operation mode will be described with reference toFIGS. 4 and 5.

When the second operation mode of the air conditioner10starts, the first and second compressors110and120are driven. Here, the “second operation mode” may be understood as a “high efficiency operation mode” or a “low load operation mode”, which is capable of performing a high efficiency operation, when a lot of circulation amounts of refrigerant are required due to a low operation load of the air conditioner. Shortly, the second operation mode may be understood as an operation mode in which an operation load that is relatively less than a preset load is needed.

When the first and second compressors110and120are driven, the refrigerant may be suctioned into the first compressor110through the first suction tube120aand suctioned in to the second compressor120through the bypass tube145. That is, in operation S21, the first and second compressors110and120operate in series.

In detail, the refrigerant compressed in the first compressor110may be introduced into the valve device140to flow to the second suction tube120bthrough the bypass tube145. Here, in operation S22, the valve device140may be controlled in the second action mode, and the refrigerant introduced into the valve device140may be restricted from flowing to the valve connection tube133and discharged to the bypass tube145through the second outlet140c.

The refrigerant in the bypass tube145may be introduced into the second suction tube120bthrough the second branch part148and suctioned into the second compressor120. Here, the refrigerant in the bypass tube145may be restricted from flowing into the compressor branch part167by the first check valve120b.

Also, since the refrigerant in the compressor branch part167has a pressure that is less than that in the second branch part148through which the refrigerant compressed in the first compressor110, the refrigerant may be restricted from flowing from the compressor branch part167to the second branch part148. Thus, the refrigerant evaporated in the evaporator190may flow to the first compressor110via the compressor branch part167.

The refrigerant compressed in the second compressor120may be introduced into the condenser150via the second discharge tube132, and the refrigerant condensed in the condenser150passes through the first main expansion device161. Here, in operation S23, the first main expansion device161may be fully opened, and thus, the refrigerant may not be decompressed while passing through the main expansion device161.

The refrigerant (the first main refrigerant) passing through the first main expansion device161is introduced into the first supercooling heat exchanger170. At least one portion of the first branch refrigerant of the first main refrigerant may be divided to flow through the first branch tube171, and the first main refrigerant may be heat-exchanged with the first branch refrigerant in the first supercooling heat exchanger170.

Here, in operation S24, the first supercooling expansion device173may be opened in a predetermined opening degree so that the first branch refrigerant flowing through the first branch tube171is decompressed.

While the decompressed first branch refrigerant is heat-exchanged with the first main refrigerant, the first branch refrigerant may be evaporated, and the first main refrigerant may be supercooled. The evaporated first branch refrigerant may be divided from the first branch part174to flow through the first and second injection tubes175and176.

The refrigerant flowing through the first injection tube175may be injected to the first injection port117of the first compressor110through the first injection expansion device177. The refrigerant injected to the first injection port117is mixed with the refrigerant compressed in the second compression part113of the first compressor110. The injection of the refrigerant to the first injection port117may be called a “high pressure-side injection” or a “second injection” of the first compressor110.

Herein in operation S25, the first expansion device177may be opened in a predetermined opening degree so that the refrigerant is decompressed.

The refrigerant flowing through the second injection tube176may be injected to the second injection port127of the second compressor120. The refrigerant injected to the second injection port127may is mixed with the refrigerant compressed in the second compression part123of the second compressor120. The injection of the refrigerant to the second injection port127may be called a “high pressure injection” or a “fourth injection” of the second compressor123. Of course, the refrigerant to be injected to the second injection port127may have a pressure that is higher than that of the refrigerant injected to the first injection port117.

The refrigerant (the second main refrigerant) passing through the first supercooling heat exchanger170may be introduced into the second supercooling heat exchanger180. At least one portion of the second branch refrigerant of the second main refrigerant may be divided to flow through the second branch tube181, and the second main refrigerant is heat-exchanged with the second branch refrigerant in the second supercooling heat exchanger180.

Here, in operation S26, the second supercooling expansion device183may be opened in a predetermined opening degree so that the second branch refrigerant flowing through the second branch tube181is decompressed.

While the decompressed second branch refrigerant is heat-exchanged with the second main refrigerant, the second branch refrigerant may be evaporated, and the second main refrigerant may be supercooled. The evaporated second branch refrigerant may be divided from the second branch part184to flow through the third and fourth injection tubes185and186.

The refrigerant flowing through the third injection tube185may be injected to the third injection port119of the first compressor110through the second injection expansion device187. The refrigerant injected to the third injection port119may is mixed with the refrigerant compressed in the first compression part111of the first compressor110. The injection of the refrigerant to the third injection port119may be called a “low pressure-side injection” or a “first injection” of the first compressor110.

Here, the second injection expansion device187may be opened in a predetermined opening degree so that the refrigerant is decompressed.

That is, in operation S27, the refrigerant in the second branch tube181is decompressed in the second supercooling expansion device183and additionally decompressed in the second injection expansion device187, and the refrigerant injected to the third injection port117may have a pressure that is less than that of the refrigerant injected to the first injection port117.

The refrigerant flowing through the fourth injection tube186may be injected to the fourth injection port129of the second compressor120. The refrigerant injected to the fourth injection port129is mixed with the refrigerant compressed in the first compression part121of the second compressor120. The injection of the refrigerant to the fourth injection port129may be called a “low pressure-side injection” or a “third injection” of the second compressor120. Of course, the refrigerant injected to the fourth injection port129may have a pressure that is higher than that of the refrigerant injected to the third injection port119.

Like this, the refrigerant passing through the first supercooling heat exchanger170may be secondly injected to the high pressure-side and the low pressure-side of the first compressor110through the injection tube, and the refrigerant passing through the second supercooling heat exchanger170may be secondly injected to the high pressure-side and the low pressure-side of the second compressor120through the injection tube.

That is, since the refrigerant is fourthly injected while the refrigerant compressed in the first compressor110is suctioned into the second compressor120through the bypass tube145and then compressed, when a pressure stage is defined with respect to the injection of the refrigerant, it may be understood that five-stage compression is performed in total.

The refrigerant passing through the second supercooling heat exchanger180may be introduced into the evaporator190through the second main expansion device165. Here, in operation S28, the second main expansion device165may be opened in a predetermined opening degree so that the refrigerant is decompressed.

The refrigerant evaporated in the evaporator190may be suctioned from the compressor branch part167to the first compressor110through the first suction tube110a. As described above, the refrigerant in the compressor branch part167may be restricted from flowing to the second combination part148by a pressure difference.

The pressure of the refrigerant in the flow of the refrigerant of the air conditioner ofFIG. 4will be simply described.

A refrigerant pressure in the compressor branch part167and the first suction tube110ais referred to as P1, a refrigerant pressure in the first discharge tube131and the second suction tube120ais referred to as P2, and a refrigerant pressure in the second discharge tube132is referred to as P3.

Also, a refrigerant pressure in the first branch part174and the second injection tube176is referred to as P4, and a pressure of the refrigerant introduced into the first injection port117after passing through the first injection expansion device177is referred to as P5.

A refrigerant pressure in the second branch part184and the fourth injection tube186is referred to as P6, and a pressure of the refrigerant introduced into the third injection port127after passing through the second injection expansion device187is referred to P7.

The following relation formula represents the size of the refrigerant pressure.
P1<P7<P5<P2<P6<P4<P3

Hereinafter, a second embodiment will be described. Since a portion of components in the current embodiment is different from that in the first embodiment, the differences will be mainly described, and the components in the current embodiment the same as those in the first embodiment quote the descriptions of the first embodiment.

Referring toFIG. 6, an air conditioner10′ according to the second embodiment includes a plurality of phase separators270and280at an outlet-side of the condenser150.

The plurality of phase separators270and280includes a first phase separator270to which a refrigerant condensed in the condenser150is introduced and separating a gaseous refrigerant from the introduced refrigerant and a second phase separator280connected in series to an outlet-side of the first phase separator270.

The gaseous refrigerant separated from the refrigerant introduced into the first phase separator270may be introduced into a first branch part174through a first discharge tube271. The first discharge tube271extends from the first phase separator270to the first branch part174. Also, the rest of the refrigerant except for the separated gaseous refrigerant may be introduced into the second phase separator280.

The refrigerant may be divided from the first branch part174and then be injected to the first compressor110through the first injection tube175and injected to the second compressor120through the injection tube176.

The second phase separator280separates the gaseous refrigerant from the refrigerant. The separated gaseous refrigerant may be introduced into a second branch part184through a second discharge tube281. The second discharge tube281extends from the second phase separator280to the second branch part184. Also, the rest of the refrigerant except for the separated gaseous refrigerant may be decompressed in the second main expansion device165and then be introduced into the evaporator190.

The refrigerant may be divided from the second branch part184and then be injected to the first compressor110through the third injection tube185and injected to the second compressor120through the fourth injection tube186.

Like this, since the gaseous refrigerant is separated by the phase separator, and the separated gaseous refrigerant is injected to the compressor, power for compressing the refrigerant in the compressor may be reduced to improve cooling and heating efficiency.

Each of the supercooling heat exchanger in the first embodiment and the phase separator in the current embodiment may separate the refrigerant to be injected to the compressor and thus be called a “refrigerant separation device”

Another embodiment is suggested.

As described above, in the first embodiment, two supercooling heat exchangers are disposed in series at an outlet-side of the condenser to perform the injection of the refrigerant, and in the second embodiment, two phase separators are disposed in series at the outlet-side of the condenser to perform the injection of the refrigerant.

Alternatively, one supercooling heat exchanger and one phase separator may be disposed in series at the outlet-side of the condenser to allow the injection of the refrigerant to be performed in the first and second compressors.

According to the present disclosure, the plurality of compressors operate in parallel or series according to the operation mode of the air conditioner.

In detail, when the air conditioner has a relatively high operation load, the first operation mode is performed, and thus, the refrigerant may be divided and suctioned into the plurality of compressors to perform the parallel operation. On the other hand, when the air conditioner has a relatively low operation load, the second operation mode is performed, and thus, the refrigerant may successively pass through the plurality of compressors to perform the series operation.

According to the operation of the air conditioner, when the first operation mode is performed, the refrigerant may be compressed in three-stages in the plurality of compressors, and thus, the amount of refrigerant circulating the air conditioner may be increased to increase refrigeration ability. Also, when the second operation mode is performed, the refrigerant may be compressed in five stages to allow the air conditioner to operation in high efficiency, and thus, the optimal operation may be controlled according to the operation mode.

Also, since the air conditioner includes the supercooling heat exchanger or the phase separator, the injection of the refrigerant of the compressor may be possible, and thus, the multi-stage compression in the compressor may be efficiently performed.

In particular, when the air conditioner includes the supercooling heat exchanger, the refrigerant may be supercooled, and thus the air conditioner may be improved in operation efficiency.

Also, since the refrigerant forming the intermediate pressure is injected to the compressor, the power for compressing the refrigerant in the compressor may be reduced to increase cooling and heating efficiency.