KR20130014740A - An air conditioner and a control method the same - Google Patents

Abstract

PURPOSE: An air conditioner and a method for controlling the same are provided to improve cooling performance by supercooling refrigerant discharged from an outdoor heat exchanger when the air conditioner is in the process of cooling. CONSTITUTION: An air conditioner comprises an outdoor unit(20), an indoor unit(30), a multi-stage compression unit(100), an inlet pipe, and a discharge tube. The multi-stage compression unit connects the outdoor unit to the indoor unit. The inlet pipe ensures refrigerant discharged from either the outdoor unit or the indoor unit to flow into the multi-stage compression unit. The discharge tube ensures the refrigerant to be discharged to either the outdoor unit or the indoor unit after passing the multi-stage compression unit. The multi-stage compression unit includes a second compressor(130) enabling additional compression for the discharged refrigerant from a first compressor and a supercooling heat exchanger(120) supercooling the condensed refrigerant from either the outdoor unit or the indoor unit. The multi-stage compression unit includes a main pipeline which carries the refrigerant through the inlet pipe, a branched pipe branched from the main pipeline, and an expansion device which expands the refrigerant flowing through the branched pipeline. [Reference numerals] (20) Outdoor unit; (30) Indoor unit

Description

Air conditioner and control method {An air conditioner and a control method the same}

The present invention relates to an air conditioner and a control method thereof.

The air conditioner is an appliance for keeping the indoor air in the most suitable condition according to the purpose and purpose. For example, in the summer, the room is controlled by a cool air condition, while in winter the room is controlled by a warm heating condition, by the humidity of the room, and by the clean air of the room.

In detail, the air conditioner is driven by a refrigeration cycle that performs the compression, condensation, expansion and evaporation process of the refrigerant, thereby performing the cooling or heating operation of the indoor space.

Such an air conditioner may be classified into a separate type air conditioner that separates the indoor unit and the outdoor unit, and an integrated air conditioner that combines the indoor unit and the outdoor unit into one device, depending on whether the indoor unit and the outdoor unit are separated.

In general, the outdoor unit includes a compressor for compressing a refrigerant, an outdoor heat exchanger for exchanging heat with the outside air, and an outdoor expansion device disposed at the outdoor side to reduce the refrigerant, and the indoor unit includes an indoor heat exchanger for exchanging heat with indoor air and an indoor side. An indoor expansion device disposed to depressurize the refrigerant.

On the other hand, when the air conditioner performs the heating operation, the amount of system refrigerant circulating the refrigeration cycle takes a lot. In this case, an input date to be input in order to achieve sufficient heating capacity, that is, a large amount of refrigerant to be sucked in the compressor is required.

However, according to the conventional air conditioner, when the air conditioner performs the heating operation, due to the limited system capacity (capacity), the amount of refrigerant circulating in the refrigerating system, in particular, the amount of refrigerant sucked into the compressor appeared to be insufficient.

Accordingly, there is a problem that the system capacity does not meet the required heating conditions (for example, increase in the amount of heating airflow, cryogenic outdoor temperature, etc.), and eventually the air conditioner does not achieve sufficient heating capacity.

In addition, when the refrigerant discharge temperature of the compressor is excessively increased according to the heating condition or the driving state of the refrigerant cycle, there is a problem that the compressor is overloaded and the heating efficiency is lowered.

On the other hand, if the degree of condensation of the refrigerant passing through the condenser, that is, the supercooling degree is not secured while the air conditioner performs the cooling operation, there is a problem that the cooling efficiency is lowered.

The present invention has been proposed to solve such a problem, and an object of the present invention is to provide an air conditioner having a multi-stage compression unit in order to improve cooling performance or heating performance.

An air conditioner according to an embodiment of the present invention includes an outdoor unit disposed in an outdoor space and having a first compressor for compressing a refrigerant and an outdoor heat exchanger for exchanging heat with outside air; An indoor unit disposed in an indoor space and having an indoor heat exchanger configured to exchange heat with indoor air; Multi-stage compression unit for connecting the outdoor unit and the indoor unit; An inlet pipe allowing the refrigerant discharged from the outdoor unit or the indoor unit to flow into the multi-stage compression unit; And a discharge pipe for discharging the refrigerant passing through the multi-stage compression unit to the outdoor unit or the indoor unit, wherein the multi-stage compression unit includes: a second compressor configured to further compress the refrigerant discharged from the first compressor; And a supercooled heat exchanger configured to overcool the refrigerant condensed in the outdoor heat exchanger or the indoor heat exchanger.

According to another aspect, a control method of an air conditioner includes: an air conditioner including an outdoor unit having a first compressor and an outdoor heat exchanger and an indoor unit having an indoor heat exchanger, wherein the refrigerant compressed by the first compressor is stored in the outdoor unit. Allowing condensation in the heat exchanger or the indoor heat exchanger; Introducing refrigerant discharged from the outdoor heat exchanger or the indoor heat exchanger into the multistage compression unit; Expanding at least some of the refrigerant introduced into the multistage compression unit; And exchanging the expanded refrigerant in a supercooled heat exchanger.

According to the present invention, since the refrigerant discharged from the outdoor heat exchanger may be supercooled while passing through the heat exchanger while the air conditioner performs the cooling operation, the cooling performance may be improved.

In addition, since the refrigerant discharged from the indoor unit may be bypassed and injected into the compressor while the air conditioner performs the heating operation, the amount of circulating refrigerant of the compressor may be increased, thereby improving heating capacity even in a poor heating condition. There is an effect.

In addition, when the discharge temperature of the compressor is increased, at least a portion of the refrigerant discharged from the indoor unit can be expanded and injected into the compressor, thereby preventing the discharge temperature of the compressor from being excessively increased and improving the heating performance. have.

As such, since the cooling and heating efficiency of the air conditioner is improved during the cooling or heating operation, reliability of the product may be improved and power consumption may be reduced.

1 is a block diagram showing the configuration of an air conditioner according to an embodiment of the present invention.
2 is a system diagram showing the configuration of a multi-stage compression unit according to an embodiment of the present invention.
3 is a system diagram showing the flow of the refrigerant in the cooling operation of the air conditioner according to an embodiment of the present invention.
4 is a system diagram showing the flow of the refrigerant during the heating operation of the air conditioner according to an embodiment of the present invention.
5 is a block diagram showing a control configuration of an air conditioner according to an embodiment of the present invention.
6 is a flowchart illustrating a control method for cooling operation of the air conditioner according to the embodiment of the present invention.
7 is a flowchart illustrating a control method for heating operation of an air conditioner according to an embodiment of the present invention.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. It is to be understood, however, that the spirit of the invention is not limited to the embodiments shown and that those skilled in the art, upon reading and understanding the spirit of the invention, may easily suggest other embodiments within the scope of the same concept.

1 is a block diagram showing the configuration of an air conditioner according to an embodiment of the present invention.

Referring to FIG. 1, a refrigeration cycle in which a refrigerant circulates is driven in the air conditioner 1 according to the embodiment of the present invention. The air conditioner 1 may be cooled or heated according to the circulation direction of the refrigerant. Hereinafter, the configuration of the air conditioner will be described based on the cooling operation.

In order to drive the refrigeration cycle, the air conditioner 1 includes an outdoor unit 20, an indoor unit 30, and a multistage compression unit 100 connecting the outdoor unit 20 and the indoor unit 30. .

The outdoor unit 20 includes a compressor 21 for compressing a refrigerant, an outdoor heat exchanger 23 for allowing the refrigerant compressed by the compressor 21 to heat exchange (condensing), and the outdoor heat exchanger 23. An outdoor expansion device 25 for expanding the condensed refrigerant is included.

The indoor unit 30 includes an indoor expansion device 35 for expanding the refrigerant introduced into the indoor unit 30 and an indoor heat exchanger 30 for allowing the refrigerant passing through the indoor expansion device 35 to heat exchange (evaporate). Included.

When the heating operation is performed, the refrigerant discharged from the compressor 21 flows into the indoor heat exchanger 30, and passes through the indoor expansion device 35 and the outdoor expansion device 25 to the outdoor heat exchanger 20. Will pass). At this time, the indoor heat exchanger 30 is a condenser, the outdoor heat exchanger 20 is to function as an evaporator.

The multi-stage compression unit 100 is configured to at least supercool the refrigerant discharged from one device of the outdoor unit 20 and the indoor unit 30 and then flow it into the other unit of the indoor unit 30 and the outdoor unit 20. .

Hereinafter, the configuration of the multi-stage compression unit 100 will be described with reference to the drawings.

2 is a system diagram showing the configuration of a multi-stage compression unit according to an embodiment of the present invention.

2, in the multi-stage compression unit 100 according to an exemplary embodiment of the present invention, a guide of the refrigerant discharged from the outdoor unit 20 or the indoor unit 30 flows into the indoor unit 30 or the outdoor unit 20. Refrigerant piping 110 is included.

The refrigerant pipe 110 includes a first inlet and outlet pipe 111 and a second inlet and outlet pipe 112 for guiding the refrigerant discharged from the outdoor unit 20 or introduced into the outdoor unit 20.

The refrigerant pipe 110 includes a third inlet and outlet pipe 113 and a fourth inlet and outlet pipe 114 for guiding the refrigerant discharged from the indoor unit 30 or introduced into the indoor unit 30.

When the air conditioner 10 performs a cooling operation, the first inlet and outlet pipe 111 is a "inlet pipe" to allow the refrigerant discharged from the outdoor unit 20 to flow into the multistage compression unit 100. It is understood that the second inlet and outlet pipe 112 may be understood as a "discharge pipe" to allow the refrigerant circulating in the multi-stage compression unit 100 to be discharged to the outdoor unit 20.

In addition, the third inlet and outlet pipe 113 is understood as a "discharge pipe" to allow the refrigerant circulating in the multi-stage compression unit 100 to be discharged to the indoor unit 30, the fourth inlet and outlet pipe 114 is The refrigerant discharged from the indoor unit 20 may be understood as an "inlet pipe" to allow the multi-stage compression unit 100 to flow into the chamber.

On the other hand, when the air conditioner 10 performs the heating operation, the first inlet and outlet pipe 111 is understood as a "discharge pipe" to allow the refrigerant to be discharged to the outdoor unit 20, the second in and out Pipe 112 may be understood as "inlet pipe" to allow the refrigerant to flow into the multi-stage compression unit 100.

And, the third inlet and outlet pipe 113 is understood as "inlet pipe" to allow the refrigerant to flow into the multi-stage compression unit 100, the fourth inlet and outlet pipe 114 is the refrigerant discharged to the indoor unit 20. It can be understood as "discharge piping" as possible.

In the multi-stage compression unit 100, an expansion device 125 and a refrigerant are expanded from the refrigerant pipe 110 so that the subcooling heat exchanger 120 and the refrigerant are expanded before the refrigerant is introduced into the subcooling heat exchanger 120. Branch pipe 123 is further included to be bypassed to (125).

The subcooling heat exchanger 120, the first heat exchanger 120a through which the refrigerant discharged from the outdoor unit 20 or the indoor unit 30 flows, and the refrigerant bypassed to the branch pipe 123 flows; 2 heat exchanger 120b is included.

The first heat exchanger 120a and the second heat exchanger 120b may be understood as part of the refrigerant pipe 110 and the branch pipe 123, respectively, or may be understood as separate heat exchange members connected to each pipe. It may be.

In the multi-stage compression unit 100, a lamination pipe 118 and a refrigerant flowing into the lamination pipe 118 to allow the refrigerant passing through the second heat exchange part 120b to be laminated with the first refrigerant pipe 110. An openable first valve 141 is included to make it possible. When the first valve 141 is opened, the refrigerant passing through the second heat exchange part 120b may be introduced into the indoor unit 30 through the lamination pipe 118 and the first valve 141.

The multistage compression unit 100 includes a second compressor 130 for compressing the refrigerant discharged from the outdoor unit 20 during the heating operation. The second compressor 130 may be understood as a “high pressure side compressor” for additionally compressing the refrigerant compressed in the first compressor 21. On the other hand, the first compressor 21 can be understood as a "low pressure side compressor".

In the multi-stage compression unit 100, an injection pipe 117 and a refrigerant guide the refrigerant passing through the second heat exchange part 120b to be introduced (injected) into the second compressor 130. A second valve 142 that can be opened to be introduced into is included. In addition, the second compressor 130 is provided with an injection port 133 into which the injection refrigerant flows. The injection pipe 117 may extend from the branch pipe 123 toward the second compressor 130.

In the heating process, since at least some of the refrigerant flowing through the refrigerant pipe 110 may be bypassed and introduced into the second compressor 130, the refrigerant circulating through the second compressor 10 may be increased. Therefore, the heating performance can be improved. In addition, since the refrigerant decompressed in the expansion device 125 may flow into the second compressor 130, the refrigerant discharge temperature of the second compressor 130 may be reduced.

In the multi-stage compression unit 100, the suction pipe 115 and the refrigerant to allow the refrigerant discharged from the outdoor unit 20 is sucked into the second compressor 130 to flow to the suction pipe 115. It further includes a third valve 143 that is openable. In addition, the second compressor 130 includes a suction port 131 through which the refrigerant flowing through the suction pipe 115 is sucked.

The second compressor 130 further includes a discharge port 132 for guiding the refrigerant discharged from the second compressor 130. One side of the discharge port 132 is provided with a fourth valve 144 that can be opened to guide the refrigerant discharged from the second compressor 130 to the indoor unit 30. The fourth valve 144 may be a check valve that prevents refrigerant from flowing into the discharge port 132 from the indoor unit 30.

In the multi-stage compression unit 100, an outdoor unit inlet pipe 116 and a refrigerant to flow the outdoor unit inlet pipe 116 to guide the refrigerant discharged from the indoor unit 30 to flow to the outdoor unit 20 side. A fifth valve 145 that is openable is included to enable it.

In the cooling process of the air conditioner 10, when the fifth valve 145 is opened, the refrigerant discharged from the indoor unit 30 may flow into the outdoor unit 20 through the outdoor unit inlet pipe 116. .

In and out pipes (111, 112, 113, 114) and a plurality of pipes (115, 116, 117, 118, 123) described above may be understood to be a configuration of the refrigerant pipe (110) in a broad sense.

Hereinafter, the refrigerant flow in the multistage compression unit 100 during the cooling or heating operation of the air conditioner 10 will be described with reference to the drawings.

3 is a system diagram showing the flow of the refrigerant in the cooling operation of the air conditioner according to an embodiment of the present invention, Figure 4 is a view showing the flow of the refrigerant in the heating operation process of the air conditioner according to an embodiment of the present invention. System drawing.

Referring to FIG. 3, the refrigerant passing through the first compressor 21 and the outdoor heat exchanger 23 of the outdoor unit 20 in the cooling process of the air conditioner is transferred to the subcooled heat exchanger through the first inlet and outlet pipe 111. Flows into 120.

In detail, at least some of the refrigerant flowing through the first entry and exit pipe 111 is branched into the branch pipe 123 and flows through the expansion device 125 to the second heat exchange part 120b. The remaining refrigerant flows to the first heat exchange part 120a except for the refrigerant branched into the branch pipe 123.

Heat exchange is performed between the first heat exchange part 120a and the second heat exchange part 120b. Since the refrigerant flowing through the branch pipe 123 is depressurized (decreased) in the expansion device 125, a predetermined heat is obtained from the first heat exchanger 120a.

Then, the refrigerant passing through the second heat exchange part 120b flows into the lamination pipe 118 and is laminated with the refrigerant flowing through the refrigerant pipe 110. In this case, the first valve 141 may be opened, and the second valve 142 may be closed.

As such, since the refrigerant may be further cooled in the subcooling heat exchanger 120 before the refrigerant enters the indoor unit 30, the cooling performance may be improved.

The laminated refrigerant may be introduced into the indoor unit 30 through the third inlet and outlet pipe 113. The refrigerant passing through the indoor heat exchanger 33 of the indoor unit 30 is introduced into the multistage compression unit 100 through the fourth inlet and outlet 114.

The refrigerant of the multistage compression unit 100 flows to the second inlet and outlet pipe 112 through the outdoor unit inlet pipe 116 and is discharged to the outdoor unit 20. At this time, the fifth valve 145 may be opened, and the third valve 143 may be closed.

Referring to FIG. 4, the refrigerant passing through the first compressor 21 of the outdoor unit 20 is introduced into the multistage compression unit 100 through the second inlet and outlet pipe 112 in the heating process of the air conditioner.

The refrigerant flows through the second inlet and outlet pipe 112 and into the suction pipe 115, and flows into the second compressor 130 through the suction port 131. At this time, the third valve 143 is opened, and the fifth valve 145 is closed.

The refrigerant introduced into the second compressor 130 is further compressed in the second compressor 130 and then introduced into the indoor unit 30 through the discharge port 132.

Meanwhile, the refrigerant introduced into the indoor unit 30 passes through the indoor heat exchanger 33 and the indoor expansion device 35, and then flows into the multistage compression unit 100 through the third inlet and outflow pipe 113. .

Then, the first heat exchanger 120a of the subcooled heat exchanger 120 flows through the refrigerant pipe 110. At this time, the first valve 141 may be closed to prevent the refrigerant from flowing into the lamination pipe 118.

At least some of the refrigerant passing through the subcooled heat exchanger 120 is bypassed to the branch pipe 123. The bypassed refrigerant flows into the second heat exchange part 120b through the expansion device 125.

The refrigerant flowing through the second heat exchange part 120b is exchanged with the refrigerant flowing through the first heat exchange part 120a, and in this process, the refrigerant flowing through the first heat exchange part 120a is supercooled. The temperature of the refrigerant flowing through the second heat exchange part 120b is increased.

The refrigerant having passed through the second heat exchange part 120b may flow into the injection pipe 117 and may be injected into the second compressor 130 through the injection port 133. At this time, the second valve 142 is opened and the first valve 141 is closed so that the refrigerant passing through the second heat exchange part 120b is prevented from flowing into the lamination pipe 118. It may flow into the injection port 133.

As such, since at least some of the refrigerant flowing in the refrigerant pipe 110 may be bypassed and injected into the second compressor 130, the amount of the refrigerant circulating in the compressor may be increased, thereby improving heating capacity. The advantage is that it can be.

On the other hand, when the discharge temperature of the second compressor 130 is abnormally increased, since the refrigerant decompressed in the expansion device 125 may be introduced into the second compressor 130, the discharge temperature can be lowered Effect occurs.

The injected refrigerant may be mixed with the refrigerant introduced through the suction port 131, compressed in the second compressor 130, and then discharged to the indoor unit 30 through the discharge port 132. At this time, the fourth valve 144 may be opened.

5 is a block diagram showing a control configuration of an air conditioner according to an embodiment of the present invention, Figure 6 is a flow chart showing a control method during the cooling operation of the air conditioner according to an embodiment of the present invention, Figure 7 is A flowchart illustrating a control method for heating operation of an air conditioner according to an embodiment of the present invention.

Referring to FIG. 5, the air conditioner 10 according to the embodiment of the present invention includes an input unit 51 capable of inputting a predetermined command relating to the operation of the air conditioner 10, and the second compressor 130. Discharge temperature sensor 52 for detecting a discharge refrigerant temperature of the air), an outside air temperature sensor 53 for detecting an outside air temperature at which the air conditioner 10 is installed, and a controller 50 for controlling these components. .

When the air conditioner 10 performs the heating operation, the heating performance required may vary depending on the outdoor air condition (heating condition). For example, the heating performance of the air conditioner when the outside air temperature is cryogenic may be lower than when the outside air temperature is relatively high.

Therefore, when the outside air temperature is lower than the set temperature, the amount of the coolant circulated to the second compressor 130 may be increased by controlling the injection of the coolant into the second compressor 130.

On the other hand, when the discharge temperature of the second compressor 130 is a high temperature higher than the set temperature, by injecting a relatively low temperature low pressure refrigerant, that is, a refrigerant passing through the expansion device 125 to the second compressor 130 The discharge temperature can be lowered.

According to the opening degree of the expansion device 125, the amount of refrigerant injected into the second compressor 130 may be adjusted. When the heating condition is not good, that is, when the outside air is a low temperature below the first set temperature or when the discharge temperature is a high temperature above the second set temperature, the opening degree of the expansion device 125 is increased to increase the second compressor ( 130 may increase the amount of the refrigerant injected into.

On the other hand, as described above, depending on whether the air conditioner 10 performs the cooling or heating operation through the operation of the input unit 51 or the like, the first valve 141 to the fifth valve 145 of the It is possible to control the circulation direction of the refrigerant by adjusting the opening and closing.

Referring to FIG. 6, a control method in the case where the air conditioner 10 performs a cooling operation will be described briefly.

The power of the air conditioner 10 is turned on, and a cooling mode is selected through the input unit 51 or the like (S11).

And, according to the cooling mode, the on / off of the flow rate control unit, that is, the plurality of valves (141 ~ 145) can be controlled. As described above, the first valve 141 and the fifth valve 145 may be opened, and the second valve 142, the third valve 143, and the fourth valve 144 may be closed ( S12).

In addition, the expansion device 125 may be turned on. The refrigerant bypassed through the branch pipe 123 is decompressed while passing through the expansion device 125 and passes through the subcooled heat exchanger 120.

The refrigerant flowing through the refrigerant pipe 110 and the refrigerant flowing through the branch pipe 123 may be laminated after heat exchange with each other, and introduced into the indoor unit 30. As a result, the refrigerant is supercooled while passing through the subcooling heat exchanger 120 and introduced into the indoor heat exchanger 33, thereby improving cooling performance (S13 and S14).

Referring to FIG. 7, a brief description will be given of a control method when the air conditioner 10 performs a heating operation.

The power of the air conditioner 10 is turned on, and the heating mode is selected through the input unit 51 (S21).

And, according to the heating mode, the flow rate control unit, that is, the on / off of the plurality of valves (141 ~ 145) can be controlled. As described above, the second valve 142, the third valve 143, and the fourth valve 144 may be opened, and the first valve 141 and the fifth valve 145 may be closed ( S22).

A heating condition (outside air condition) may be recognized through the outside temperature sensor 53, and a discharge refrigerant temperature of the second compressor 130 may be recognized through the discharge temperature sensor 52. The amount of refrigerant to be injected into the second compressor 130 may be determined by the heating condition or the discharge temperature.

According to the detected heating condition or the discharge temperature, ON / OFF of the expansion device 125 may be controlled. In addition, by opening the second valve 142, the refrigerant decompressed in the expansion device 125 may be injected into the second compressor 130.

In detail, when the expansion device 125 is turned on, the refrigerant bypassed through the branch pipe 123 is decompressed while passing through the expansion device 125 and passes through the subcooling heat exchanger 120.

The refrigerant passing through the subcooling heat exchanger 120 may be injected into the second compressor 130 to increase the amount of the refrigerant circulating through the second compressor 130. In this case, heating performance may be improved or the discharge refrigerant temperature of the second compressor 130 may be reduced.

In addition, the amount of the refrigerant injected into the second compressor 130 may vary according to the opening degree of the expansion device 125.

For example, when the heating condition is not good, that is, when the outside temperature is cryogenic or the discharge temperature is higher than the set temperature, the opening degree of the expansion device 125 is increased so that the refrigerant injected into the second compressor 130 is increased. The amount can be increased (S23, S24, S25).

As described above, by injecting a part of the refrigerant circulating in the refrigerant system into the compressor in the heating operation mode, the amount of the refrigerant circulating in the compressor can be increased, thereby improving heating capacity and reducing the discharge temperature of the compressor. The effect is that it can.

10: air conditioner 20: outdoor unit
21: first compressor 23: outdoor heat exchanger
25: outdoor expansion device 30: indoor unit
33: indoor heat exchanger 35: indoor expansion device
100: multi-stage compression unit 110: refrigerant piping
111, 112, 113, 114: incoming and outgoing piping 120: supercooled heat exchanger
130: second compressor 141, 142, 143, 144, 145 valve

Claims (12)

An outdoor unit disposed in an outdoor space, the outdoor unit including a first compressor for compressing a refrigerant and an outdoor heat exchanger for exchanging heat with outside air;
An indoor unit disposed in an indoor space and having an indoor heat exchanger configured to exchange heat with indoor air;
Multi-stage compression unit for connecting the outdoor unit and the indoor unit;
An inlet pipe allowing the refrigerant discharged from the outdoor unit or the indoor unit to flow into the multi-stage compression unit; And
It includes a discharge pipe for discharging the refrigerant passing through the multi-stage compression unit to the outdoor unit or indoor unit,
The multistage compression unit,
A second compressor configured to further compress the refrigerant discharged from the first compressor; And
And a supercooled heat exchanger configured to supercool the refrigerant condensed in the outdoor heat exchanger or the indoor heat exchanger. The method of claim 1,
The multistage compression unit,
A main pipe through which the refrigerant passing through the inflow pipe flows;
A branch pipe branched from the main pipe; And
Air conditioner further comprises an expansion device for expanding the refrigerant flowing through the branch pipe. The method of claim 2,
And the refrigerant passing through the expansion device is heat-exchanged with the condensed refrigerant in the subcooling heat exchanger. The method of claim 3, wherein
In the heating mode, air conjoined, the refrigerant heat exchanged with the condensed refrigerant is introduced into the second compressor. The method of claim 1,
In heating mode, the refrigerant compressed in the first compressor is further compressed in the second compressor. The method of claim 3, wherein
In the cooling mode, the condensed refrigerant and the heat exchanged refrigerant is characterized in that the laminated to the main pipe. The method of claim 2,
Further comprising a discharge temperature sensor for detecting the discharge refrigerant temperature of the second compressor and an outside temperature sensor for detecting the temperature of the outside air,
The expansion device is an air conditioner, characterized in that the opening degree is adjusted based on the temperature value recognized by the discharge temperature sensor or the outside temperature sensor. An air conditioner including an outdoor unit provided with a first compressor and an outdoor heat exchanger and an indoor unit provided with an indoor heat exchanger,
Allowing the refrigerant compressed in the first compressor to condense in the outdoor heat exchanger or the indoor heat exchanger;
Introducing refrigerant discharged from the outdoor heat exchanger or the indoor heat exchanger into the multistage compression unit;
Expanding at least some of the refrigerant introduced into the multistage compression unit; And
And the heat exchanged heat exchanger in the supercooled heat exchanger. The method of claim 8,
In the cooling mode,
The expanded portion of the refrigerant control method of the air conditioner, characterized in that the heat exchange with the remaining refrigerant of the refrigerant introduced into the multi-stage compression unit. The method of claim 9,
And after the expanded refrigerant is heat-exchanged in the subcooling heat exchanger, laminating with the remaining refrigerant. The method of claim 8,
In heating mode,
And the refrigerant exchanged in the subcooled heat exchanger is introduced into a second compressor. The method of claim 11,
In heating mode,
And the refrigerant compressed in the first compressor is further compressed in the second compressor.

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